Highly efficient OLED devices with very short decay times

ABSTRACT

The present invention relates to organic light-emitting devices comprising (a) an anode, (i) a cathode, and (e) an emitting layer between the anode and cathode, comprising 2 to 40% by weight of a luminescent organometallic complex X having a difference of the singlet energy (E S1 (X)) and the triplet energy (E T1 (X)) of smaller than 0.2 eV [Δ (E S1 (X))−(E T1 (X))&lt;0.2 eV], 0.05 to 5.0% by weight of a fluorescent emitter Y and 55 to 97.95% by weight of a host compound(s), wherein the amount of the organometallic complex X, the fluorescent emitter Y and the host compound(s) adds up to a total of 100% by weight and the singlet energy of the luminescent organometallic complex X (E S1 (X)) is greater than the singlet energy of the fluorescent emitter Y (E S1 (Y)) [(E S1 (X))&gt;E S1 (Y)]. By doping, for example, an emitting layer containing a luminescent organometallic complex having a small S 1 -T 1  splitting, with a fluorescent emitter the emission decay time can significantly be shortened without sacrificing external quantum efficiency (EQE) because of very efficient energy transfer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application (under 35 U.S.C. § 371)of PCT/EP2014/078342, filed Dec. 17, 2014, which claims the benefit ofEuropean Application No. 13198990.7, filed Dec. 20, 2013, both of whichare incorporated herein by reference in their entirety.

The present invention relates to organic light-emitting devicescomprising (a) an anode, (i) a cathode, and (e) an emitting layerbetween the anode and cathode, comprising 2 to 40% by weight of aluminescent organometallic complex X having a difference of the singletenergy (E_(S1)(X)) and the triplet energy (E_(T1)(X)) of smaller than0.2 eV [Δ (E_(S1)(X))−(E_(T1)(X))<0.2 eV], 0.05 to 5.0% by weight of afluorescent emitter Y and 55 to 97.95% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weightand the singlet energy of the luminescent organometallic complex X(E_(S1)(X)) is greater than the singlet energy of the fluorescentemitter Y (E_(S1)(Y)) [E_(S1)(X))>E_(S1)(Y)].

In EP1705727A a concept is described, as, despite the intrinsicallylimited to 25% quantum efficiency of direct light emission of afluorescent blue emitter, the overall efficiency of a white-light OLEDcan be made to 100%, by using a fluorescent blue emitter with a tripletenergy, which is higher than the triplet energy of at least onephosphorescent emitter used. By diffusion of the non-radiative tripletexcitons through the blue emitting layer to a further emission layercontaining the phosphorescent emitter, and subsequent exothermic energytransfer the triplet excitons of the blue emitter may be used for lightemission. In conclusion in this case, a transfer from the fluorescent tothe phosphoreszent compound is described.

WO0108230 relates to organic light emitting devices (OLED) comprising aheterostructure for producing luminescence, comprising an emissivelayer,

wherein the emissive layer is a combination of a conductive hostmaterial and a fluorescent emissive molecule, such as, for example,DCM2, present as a dopant in said host material:

wherein the emissive molecule is adapted to luminesce when a voltage isapplied across the heterostructure; and

wherein the heterostructure comprises an intersystem crossing molecule,such as, for example, Ir(ppy)₃, which is an efficient phosphor whoseemission spectrum substantially overlaps with the absorption spectrum ofthe emissive molecule.

In FIG. 1 an OLED is shown with alternating thin layers (5×) of CBP(89%) and Ir(ppy)₃ (11%) and CBP (99%) and DCM2 (1%), respectively.

WO2008131750 discloses organic light emitting devices, wherein theemission layer comprises at least one mainly emitting in the blue orblue-green spectrum light, fluorescent emitter and at least onepredominantly in the non-blue spectral light emitting phosphorescentemitter. The observed small decrease in the quantum efficiency isexplained as follows: The problem, that a large accumulation of tripletexcitons is produced at the necessary high current densities in thefluorescent emission layer, resulting in the efficiency of the so-called“roll-off” effect, is solved by the direct blending of one or morephosphorescent emitter, since thus the triplet formed on one or allfluorescent emitters are transferred directly to the phosphorescentemitter and the triplet-triplet accumulation cannot arise.

US2011108769 (WO2010006681) proposes a so-called “singlet harvesting”process. The T₁ state is occupied by the already known effects oftriplet harvesting, and the usual T₁→S₀ phosphorescence results, butwith the unfavourably long emission lifetime. The complex compoundsproposed for use in accordance with US2011108769 have a very smallenergetic separation ΔE between the singlet S₁ and the triplet T₁. Inthis case, very efficient thermal re-occupation from the initially veryefficiently occupied T₁ state into the S₁ state can occur at roomtemperature. The thermal re-occupation process described opens a fastemission channel from the short-lived S₁ state, and the overall lifetimeis significantly reduced.

M. A. Baldo et al., Nature 403 (2000) 750 use a phosphorescentsensitizer to excite a fluorescent dye. The mechanism for energeticcoupling between phosphorescent and fluorescent molecular species is along-range, non-radiative energy transfer: the internal efficiency offluorescence can be as high as 100%. In FIG. 1 of M. A. Baldo et al.,Nature 403 (2000) 750 an organic light emitting device having thefollowing structure is shown: glass substrate/indium tin oxide(anode)/N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD, hole transport layer)/10 alternating layers of 10% Ir(ppy)3/CBPand 1% DCM2/CBP/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP,blocking layer)/tris-(8-hydroxyquinoline) aluminium (Alq3, electrontransport layer)/Mg/Ag (cathode). The intermolecular energy transfer isdominated by the slow transfer rate out of the T₁-state of the donor(FIG. 1a ). Since intersystem crossing is very fast (−fs) also thesinglet states end up in the T₁-state, which therefore limits the rateof the transfer due to its partly forbidden nature. The sensitizedelectroluminescence (EL) decay time is measured to be around 100 ns.Measurements of the EL decay time in devices is hindered by secondaryprocesses such as charge transport (depending on charge mobility),trapping processes and capacitive processes, which leads to distortionsof the radiative decay time of the excited states of emitter species,especially in the range equal, or smaller than 200 ns. Therefore ameasurement of the EL decay kinetics is not instructive for determiningemissive decay times in the present invention.

M. A. Baldo et al., APPLIED PHYSICS LETTERS 79 (2001) reportshigh-efficiency yellow organic light-emitting devices (OLEDs) employing[2-methyl-6-[2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinolizin-9-yl]ethenyl]-4H-pyran-4-ylidene]propane-dinitrile (DCM2) as a fluorescent lumophore, with a greenelectrophosphorescent sensitizer, fac-tris(2-phenylpyridine) iridium(Ir(ppy)3) co-doped into a 4,4′-N,N-dicarbazole-biphenyl host. Thedevices exhibit peak external fluorescent quantum and power efficienciesof 9%±1% (25 cd/A) and 17±2 lm/W at 0.01 mA/cm², respectively. Theexceptionally high performance for a fluorescent dye is due to the ˜100%efficient transfer of both singlet and triplet excited states in thedoubly doped host to the fluorescent material using Ir(ppy)₃ as asensitizing agent.

X. Zhu et al., Journal of Luminescence 132 (2012) 12-15 disclosePVK-based single-layer phosphorescent polymer OLEDs (organic lightemitting diodes) with different rubrene concentrations. The structure offabricated devices was: ITO/PEDOT:PSS/PVK+Flr-pic(bis[(4,6-difluorophenyl)-pyridinato-N,C²](picolinate)iridium(III))+rubrene (5,6,11,12-tetraphenylnaphthacene)+OXD7/LiF/Al.PVK (poly(N-vinylcarbazole)) is used as a hole transporting host polymerand OXD7 (3-bis (4-tert-butylphenyl-1,3,4-oxadiazoyl)phenylene) is usedas an electron transporting moiety. The weight ratio of PVK:OXD7 was2.56:1 and the weight percent of Flrpic was 10 wt % of total amount oforganics. The amount of rubrene was varied from 0 to 10 wt % of Flrpic.Below 2% doping of rubrene the emission from rubrene was hardlydetected. At 4% doping of rubrene, however, significant energy transferfrom Flrpic to rubrene occurred.

Zisheng Su et al., J. Phys. D: Appl. Phys. 41 (2008) 125108 reportimproved efficiency and colour purity of blue electrophosphorescentdevices based on Flrpic by codoping a fluorescent emitter2,5,8,11-tetra-t-butyl-perylene (TBPe). The optimized device codopedwith 8 wt % Flrpic and 0.15 wt % TBPe shows a maximum current efficiencyand power efficiency of 11.6 cd A⁻¹ and 7.3 ImW⁻¹, which were increasedby 20% and 40%, respectively, compared with that of the referencedevice.

The devices have a structure of ITO/2-TNATA (5 nm)/NPB (40nm)/mCP:Flrpic:TBPe (30 nm)/Bphen (10 nm)/Alq3 (20 nm)/LiF (0.5 nm)/Al(100 nm). The doping concentration of Flrpic in the EML was fixed at 8wt %, while the concentration of TBPe was varied from 0 to 0.5 wt %.

With a few exceptions, the electronic excited state, which can also beformed by energy transfer from a suitable precursor exciton, is either asinglet or triplet state, consisting of three sub-states. Since the twostates are generally occupied in a ratio of 1:3 on the basis of spinstatistics, the result is that the emission from the singlet state,which is referred to as fluorescence, leads to maximum emission of only25% of the excitons produced. In contrast, triplet emission, which isreferred to as phosphorescence, exploits and converts all excitons andemits them as light (triplet harvesting) such that the internal quantumyield in this case can reach the value of 100%, provided that theadditionally excited singlet state, which is above the triplet state interms of energy, relaxes fully to the triplet state (intersystemcrossing, ISC), and radiationless competing processes remaininsignificant.

The triplet emitters suitable for triplet harvesting used are generallytransition metal complexes in which the metal is selected from the thirdperiod of the transition metals and which show emission lifetimes in theμs range. The long decay times of the triplet emitters give rise tointeraction of triplet excitons (triplet-triplet annihilation), orinteraction of triplet-polaron interaction (triplet-polaron quenching).This leads to a distinct decline in efficiency of the OLED device withrising current density (called “roll-off” behavior). For instance,disadvantages are found particularly in the case of use of emitters withlong emission lifetimes for OLED illuminations where a high luminance,for example of more than 1000 cd/m², is required (cf.: J.

Kido et al. Jap. J. Appl. Phys. 2007, 46, L10.). Furthermore, moleculesin electronically excited states are frequently more chemically reactivethan in ground states so that the likelihood of unwanted chemicalreactions increases with the length of the emission lifetime. Theoccurrence of such unwanted chemical reactions has a negative effect onthe lifetime of the device.

Thus, it is the object of the present invention to provide an emittingsystem which makes use of 100% of the triplet excitons and enables decaytimes below 100 ns, which result in an increased stability of theemitting system.

It was surprisingly found that doping, for example, an emitting layercontaining a luminescent organometallic complex having a small S₁-T₁splitting, with a fluorescent emitter can significantly shorten theemission decay time well below 100 ns without sacrificing externalquantum efficiency (EQE) because of very efficient energy transfer (FIG.1b ). Here the transfer originates mainly from the singlet state of thedonor molecule in contrast to the scenario shown in FIG. 1a . Additionalpositive effects can be an improved OLED stability and a lower roll-offat high luminance.

Accordingly, the present invention relates to organic electronicdevices, especially organic light-emitting devices comprising

(a) an anode,

(i) a cathode, and

(e) an emitting layer between the anode and cathode, comprising

2 to 40% by weight of a luminescent organometallic complex X having adifference of the singlet energy (E_(S1)(X)) and the triplet energy(E_(T1)(X)) of smaller than 0.2 eV [Δ (E_(S1)(X))−(E_(T1)(X))<0.2 eV],

0.05 to 5.0% by weight of a fluorescent emitter Y and

55 to 97.95% by weight of a host compound(s), wherein the amount of theorganometallic complex X, the fluorescent emitter Y and the hostcompound(s) adds up to a total of 100% by weight and the singlet energyof the luminescent organometallic complex X (E_(S1)(X)) is greater thanthe singlet energy of the fluorescent emitter Y (E_(S1)(Y))[(E_(S1)(X))>E_(S1)(Y)].Determination of the S₁-T₁-splitting

To determine the S₁-T₁-splitting a combined approach involvingtemperature dependent determination of excited state lifetimes andquantum chemical calculations are used.

a) Experimental Approach

A 60 μm thin film of the luminescent organometallic complex X in PMMA(2%) is prepared by doctor blading from dichloromethane onto a quartzsubstrate. A cryostat (Optistat CF, Oxford Instruments) is used forcooling the sample with liquid helium. The photoluminescence (PL)spectra and the PL decay time at the maximum of the emission aremeasured with a spectrometer (Edinburgh Instruments FLS 920P) at thefollowing temperatures: 4K, 10K, 20K, 30K, 50K, 75K, 100K, 150K, 200K,250K, 300K, 350K, 375K, 400K.

Fitting:

The temperature dependence of the averaged PL decay time providesinformation about the energy levels and decay rates of different statesthat are populated according to the Boltzmann distribution (M. J. Leitl,V. A. Krylova, P. I. Djurovich, M. E. Thompson, H. Yersin J. Am. Chem.Soc. 2014, 136, 16032-16038; T. Hofbeck, H. Yersin, Inorg. Chem. 2010,49, 9290-9299). For a system with two populated excited states thefollowing expression can be fitted to the measured data k_(av) vs T:

$\begin{matrix}{k_{av} = \frac{k_{I} + {k_{II}e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}}}{1 + e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

For a system with three populated excited states equation 2 is used.

$\begin{matrix}{k_{av} = \frac{k_{I} + {k_{II}e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}} + {k_{III}e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}}}{1 + e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}} + e^{{- \Delta}\; E_{I,{II}}{I{({K_{B}T})}}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

where k_(av) is the decay rate determined from the measurement, k_(I),k_(II), k_(III) are the decay rates of the respective excited states,E_(I,II) and E_(I,III) are the energy differences of the excited statesI and II compared to the lowest excited state, k_(B) is the Boltzmannconstant and T is the temperature.

A high value of k (>2*10⁶ s⁻¹) is an indication that the respectiveexcited state could be a singlet. However, since the spin multiplicityof the excited states cannot be proven by PL measurements, additionalquantum chemical calculations were carried out and compared to theexcited-state levels found from the fitting of the measurement.

b) Quantum Chemical Approach

First the triplet geometries of the potential donor molecules wereoptimized at the unrestricted BP86 [J. P. Perdew, Phys. Rev. B 33, 8822(1986) and J. P. Perdew, Phys. Rev. B 33, 8822 (1986)]/SV(P) [A.Schafer, H. Horn, and R. Ahlrichs, J. Chem. Phys. 9, 2571 (1992)]-levelof theory including effective core potentials in case of iridiumtransition metal complexes [D. Andrae, U. Haeussermann, M. Dolg, H.Stoll, and H. Preuss, Theor. Chim. Acta 77, 123 (1990)]. Based on thesetriplet geometries relativistic all electron calculations were performedto determine the S₁-T₁-splitting. Specifically we used theB3LYP-functional [Becke, A. D., J. Chem. Phys. 98, 5648 (1993)] incombination with an all-electron basis set of double zeta quality [E.van Lenthe and E. J. Baerends, J. Comp. Chemistry 24, 1142 (2003)].Scalar relativistic effects were included at the SCF level via the ZORAapproach [E. van Lenthe, A. E. Ehlers and E. J. Baerends, Journal ofChemical Physics 110, 8943 (1999)]. Based on that wavefunction timedependent density functional calculations were performed including spinorbit coupling via perturbation theory [F. Wang and T. Ziegler, Journalof Chemical Physics 123, 154102 (2005)]. The S₁-T₁-splitting is thenfinally determined as the energy difference of the lowest T₁-sublevel tothe first spin-orbit corrected S₁-state. Relativistic calculations werecarried out using the ADF program package [3. ADF2009.01, SCM,Theoretical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands,http://www.scm.com] whereas for the geometry optimisations the TURBOMOLEprogram package [R. Ahlrichs, M. Bär, M. Häser, H. Horn, and C. Cölmel,Chem. Phys. Lett. 162, 165 (1989)] was used. According to the presentinvention the difference of the singlet energy (E_(S1)(X)) and thetriplet energy (E_(T1)(X)) is the experimentally determined value.

The present invention is also directed to the use of a fluorescentemitter Y for doping an emitting layer comprising a luminescentorganometallic complex X having a difference of the singlet energy(E_(S1)(X)) and the triplet energy (E_(T1)(X)) of smaller than 0.2 eV [Δ(E_(S1)(X))−(E_(T1)(X))<0.2 eV] and having a singlet energy (E_(S1)(X))which is greater than the singlet energy of the fluorescent emitter Y(E_(S1)(Y)) [(E_(S1)(X))>E_(S1)(Y)] and a host compound(s) to decreasethe decay time of the emission below 100 ns.

Determination of Emissive Lifetime

In accordance with the present invention the decay time of the emissionis the emissive lifetime to, which is calculated by τ₀=τ_(v)/QY, of thinfilms consisting of the luminescent organometallic complex X (2 to 40%by weight), fluorescent emitter Y (0.05 to 5.0% by weight) and hostcompound(s) (55 to 97.95% by weight). The quantum-yields (QY) of theprepared thin films are measured with the integrating-sphere methodusing the Absolute PL Quantum Yield Measurement System (Hamamatsu, ModelC9920-02) (excitation wavelength: 310 nm).

The excited-state lifetime (τ_(v)) of the prepared thin films ismeasured by exciting the thin films with a pulsed diode laser with anexcitation wavelength of 310 nm operated at 10 kHz and detecting theemission with time correlated single photon counting (TCSPC).

The emissive lifetime τ₀ is preferably in the range of 0.1 to 80 ns,more preferably 0.5 to 50 ns, most preferred 0.5 to 40 ns.

The difference of the singlet energy and the triplet energy of theluminescent organometallic complex X is preferably smaller than 0.1 eV,more preferably smaller than 0.05 eV.

Preferably, the emitting layer comprises 5 to 40% by weight of theluminescent organometallic complex X, 0.1 to 4.0% by weight of thefluorescent emitter Y and 94.9 to 56.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.More preferably, the emitting layer comprises 10 to 40% by weight of theluminescent organometallic complex X, 0.1 to 3.0% by weight of thefluorescent emitter Y and 89.9 to 57.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.Most preferred, the emitting layer comprises 20 to 40% by weight of theluminescent organometallic complex X, 0.1 to 3.0% by weight of thefluorescent emitter Y and 79.9 to 57.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.

FIG. 1a shows an energy level diagram demonstrating that intermoleculartransfer is dominated by the slow transfer rate out of the T₁-state ofthe donor.

FIG. 1b shows an energy level diagram for the fluorescent emitter Y(=donor) and the luminescent organometallic complex X (acceptor) usedaccording to the present invention.

FIG. 2 shows PL-spectra of 2% luminescent organometallic complex BE-24and varying concentrations of the fluorescent emitter FE-1 in PMMA

FIG. 3 shows PL-spectra of 2% luminescent organometallic complex BE-24and varying concentrations of the fluorescent emitter FE-2 in PMMA.

Suitable structures of organic light emitting devices are known to thoseskilled in the art and are specified below.

Substrate may be any suitable substrate that provides desired structuralproperties. Substrate may be flexible or rigid. Substrate may betransparent, translucent or opaque. Plastic and glass are examples ofpreferred rigid substrate materials. Plastic and metal foils areexamples of preferred flexible substrate materials. Substrate may be asemiconductor material in order to facilitate the fabrication ofcircuitry. For example, substrate may be a silicon wafer upon whichcircuits are fabricated, capable of controlling organic light emittingdevices (OLEDs) subsequently deposited on the substrate. Othersubstrates may be used. The material and thickness of substrate may bechosen to obtain desired structural and optical properties.

In a preferred embodiment the organic light-emitting device according tothe present invention comprises in this order:

(a) an anode,

(b) optionally a hole injection layer,

(c) optionally a hole transport layer,

(d) optionally an exciton blocking layer

(e) an emitting layer, comprising the luminescent organometallic complexX, the fluorescent emitter Y and the host compound(s),

(f) optionally a hole/exciton blocking layer

(g) optionally an electron transport layer,

(h) optionally an electron injection layer, and

(i) a cathode.

In a particularly preferred embodiment the organic light-emitting deviceaccording to the present invention comprises in this order:

(a) an anode,

(b) optionally a hole injection layer,

(c) a hole transport layer,

(d) an exciton blocking layer

(e) an emitting layer, comprising the luminescent organometallic complexX, the fluorescent emitter Y and the host compound(s),

(f) a hole/exciton blocking layer

(g) an electron transport layer, and

(h) optionally an electron injection layer, and

(i) a cathode.

The properties and functions of these various layers, as well as examplematerials are known from the prior art and are described in more detailbelow on basis of preferred embodiments.

Anode (a):

The anode is an electrode which provides positive charge carriers. Itmay be composed, for example, of materials which comprise a metal, amixture of different metals, a metal alloy, a metal oxide or a mixtureof different metal oxides. Alternatively, the anode may be a conductivepolymer. Suitable metals comprise the metals of groups 11, 4, 5 and 6 ofthe Periodic Table of the Elements, and also the transition metals ofgroups 8 to 10. When the anode is to be transparent, mixed metal oxidesof groups 12, 13 and 14 of the Periodic Table of the Elements aregenerally used, for example indium tin oxide (ITO). It is likewisepossible that the anode (a) comprises an organic material, for examplepolyaniline, as described, for example, in Nature, Vol. 357, pages 477to 479 (Jun. 11, 1992). Preferred anode materials include conductivemetal oxides, such as indium tin oxide (ITO) and indium zinc oxide(IZO), aluminum zinc oxide (AlZnO), and metals. Anode (and substrate)may be sufficiently transparent to create a bottom-emitting device. Apreferred transparent substrate and anode combination is commerciallyavailable ITO (anode) deposited on glass or plastic (substrate). Areflective anode may be preferred for some top-emitting devices, toincrease the amount of light emitted from the top of the device. Atleast either the anode or the cathode should be at least partlytransparent in order to be able to emit the light formed. Other anodematerials and structures may be used.

Hole Injection Layer (b):

Generally, injection layers are comprised of a material that may improvethe injection of charge carriers from one layer, such as an electrode ora charge generating layer, into an adjacent organic layer. Injectionlayers may also perform a charge transport function. The hole injectionlayer may be any layer that improves the injection of holes from anodeinto an adjacent organic layer. A hole injection layer may comprise asolution deposited material, such as a spin-coated polymer, or it may bea vapor deposited small molecule material, such as, for example, CuPc orMTDATA. Polymeric hole-injection materials can be used such aspoly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole, polyaniline,self-doping polymers, such as, for example, sulfonatedpoly(thiophene-3-[2[(2-methoxyethoxy)ethoxy]-2,5-diyl) (Plexcore® OCConducting Inks commercially available from Plextronics), and copolymerssuch as poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) alsocalled PEDOT/PSS.

Hole Transport Layer (c):

Either hole-transporting molecules or polymers may be used as the holetransport material. Suitable hole transport materials for layer (c) ofthe inventive OLED are disclosed, for example, in Kirk-OthmerEncyclopedia of Chemical Technology, 4th Edition, Vol. 18, pages 837 to860, 1996, US20070278938, US2008/0106190, US2011/0163302 (triarylamineswith (di)benzothiophen/(di)benzofuran; Nan-Xing Hu et al. Synth. Met.111 (2000) 421 (indolocarbazoles), WO2010002850 (substituted phenylaminecompounds) and WO2012/16601 (in particular the hole transport materialsmentioned on pages 16 and 17 of WO2012/16601). Combination of differenthole transport material may be used. Reference is made for example, toWO2013/022419, wherein

constitute the hole transport layer.

Customarily used hole-transporting molecules are selected from the groupconsisting of

(4-phenyl-N-(4-phenylphenyl)-N-[4-[4-(N-[4-(4-phenyl-phenyl)phenyl]anilino)phenyl]phenyl]aniline),

(4-phenyl-N-(4-phenylphenyl)-N-[4-[4-(4-phenyl-N-(4-phenylphenyl)anilino)phenyl]phenyl]aniline),

(4-phenyl-N-[4-(9-phenylcarbazol-3-yl)phenyl]-N-(4-phenylphenyl)aniline),

(1,1′,3,3′-tetraphenylspiro[1,3,2-benzodiazasilole-2,2′-3a,7a-dihydro-1,3,2-benzodiazasilole]),

(N2,N2,N2′,N2′,N7,N7,N7′,N7′-octa-kis(p-tolyl)-9,9′-spirobi[fluorene]-2,2′,7,7′-tetramine),4,4′-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD),N,N′-diphenyl-N,N′-bis(3-methylphenyl)-[1,1′-biphenyl]-4,4′-diamine(TPD), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC),N,N′-bis(4-methylphenyl)-N,N′-bis(4-ethylphenyl)-[1,1′-(3,3′-dimethyl)biphenyl]-4,4′-diamine(ETPD), tetrakis(3-methylphenyl)-N,N,N′,N′-2,5-phenylenediamine (PDA),α-phenyl-4-N,N-diphenylaminostyrene (TPS), p-(diethylamino)benzaldehydediphenyl-hydrazone (DEH), triphenylamine (TPA),bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)methane (MPMP),1-phenyl-3-[p-(diethylamino)styryl]-5-[p-(diethylamino)phenyl]pyrazoline(PPR or DEASP), 1,2-trans-bis(9H-carbazol-9-yl)-cyclobutane (DCZB),N,N,N′,N′-tetrakis(4-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TTB),fluorine compounds such as2,2′,7,7′-tetra(N,N-di-tolyl)amino9,9-spirobifluorene (spiro-TTB),N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)9,9-spirobifluorene(spiro-NPB) and9,9-bis(4-(N,N-bis-biphenyl-4-yl-amino)phenyl-9Hfluorene, benzidinecompounds such as N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)benzidineand porphyrin compounds such as copper phthalocyanines. In addition,polymeric hole-injection materials can be used such aspoly(N-vinylcarbazole) (PVK), polythiophenes, polypyrrole, polyaniline,self-doping polymers, such as, for example, sulfonatedpoly(thiophene-3-[2[(2-methoxyethoxy)ethoxy]-2,5-diyl) (Plexcore® OCConducting Inks commercially available from Plextronics), and copolymerssuch as poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) alsocalled PEDOT/PSS. In a preferred embodiment it is possible to use metalcarbene complexes as hole transport materials. Suitable carbenecomplexes are, for example, carbene complexes as described inWO2005/019373A2, WO2006/056418 A2, WO2005/113704, WO2007/115970,WO2007/115981, WO2008/000727 and WO2014/147134. One example of asuitable carbene complex is Ir(DPBIC)₃ with the formula:

Another example of a suitable carbene complex is Ir(ABIC)₃ with theformula:

The hole-transporting layer may also be electronically doped in order toimprove the transport properties of the materials used, in order firstlyto make the layer thicknesses more generous (avoidance of pinholes/shortcircuits) and in order secondly to minimize the operating voltage of thedevice. Electronic doping is known to those skilled in the art and isdisclosed, for example, in W. Gao, A. Kahn, J. Appl. Phys., Vol. 94,2003, 359 (p-doped organic layers); A. G. Werner, F. Li, K. Harada, M.Pfeiffer, T. Fritz, K. Leo, Appl. Phys. Lett., Vol. 82, No. 25, 2003,4495 and Pfeiffer et al., Organic Electronics 2003, 4, 89-103 and K.Walzer, B. Maennig, M. Pfeiffer, K. Leo, Chem. Soc. Rev. 2007, 107,1233. For example it is possible to use mixtures in thehole-transporting layer, in particular mixtures which lead to electricalp-doping of the hole-transporting layer. p-Doping is achieved by theaddition of oxidizing materials. These mixtures may, for example, be thefollowing mixtures: mixtures of the abovementioned hole transportmaterials with at least one metal oxide, for example MoO₂, MoO₃, WO_(x),ReO₃ and/or V₂O₅, preferably MoO₃ and/or ReO₃, more preferably MoO₃, ormixtures comprising the aforementioned hole transport materials and oneor more compounds selected from 7,7,8,8-tetracyanoquinodimethane (TCNQ),2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F₄-TCNQ),2,5-bis(2-hydroxyethoxy)-7,7,8,8-tetracyanoquinodimethane,bis(tetra-n-butylammonium)tetracyanodiphenoquinodimethane,2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane, tetracyanoethylene,11,11,12,12-tetracyanonaphtho-2,6-quinodimethane,2-fluoro-7,7,8,8-tetracyanoquino-dimethane,2,5-difluoro-7,7,8,8-etracyanoquinodimethane,dicyanomethylene-1,3,4,5,7,8-hexafluoro-6H-naphthalen-2-ylidene)malononitrile(F₆-TNAP), Mo(tfd)₃ (from Kahn et al., J. Am. Chem. Soc. 2009, 131 (35),12530-12531), compounds as described in EP1988587, US2008265216,EP2180029, US20100102709, WO2010132236, EP2180029 and quinone compoundsas mentioned in EP2401254. Preferred mixtures comprise theaforementioned carbene complexes, such as, for example, the carbenecomplexes HTM-1 and HTM-2, and MoO₃ and/or ReO₃, especially MoO₃. In aparticularly preferred embodiment the holetransport layer comprises from0.1 to 10 wt % of MoO₃ and 90 to 99.9 wt % carbene complex, especiallyof a carbene complex HTM-1 and HTM-2, wherein the total amount of theMoO₃ and the carbene complex is 100 wt %.

Exciton Blocking Layer (d):

Blocking layers may be used to reduce the number of charge carriers(electrons or holes) and/or excitons that leave the emissive layer. Anelectron/exciton blocking layer (d) may be disposed between the emittinglayer (e) and the hole transport layer (c), to block electrons fromemitting layer (e) in the direction of hole transport layer (c).Blocking layers may also be used to block excitons from diffusing out ofthe emissive layer. Suitable metal complexes for use as electron/excitonblocker material are, for example, carbene complexes as described inWO2005/019373A2, WO2006/056418A2, WO2005/113704, WO2007/115970,WO2007/115981, WO2008/000727 and WO2014/147134. Explicit reference ismade here to the disclosure of the WO applications cited, and thesedisclosures shall be considered to be incorporated into the content ofthe present application. One example of a suitable carbene complex iscompound HTM-1. Another example of a suitable carbene complex iscompound HTM-2.

The Light-Emitting Layer (e)

The device comprises a light-emitting layer (e).

The emitting layer comprises

2 to 40% by weight of a luminescent organometallic complex X having adifference of the singlet energy and the triplet energy of smaller than0.2 eV, 0.05 to 5% by weight of a fluorescent emitter Y and

55 to 97.95% by weight of a host compound(s), wherein the amount of theorganometallic complex X, the fluorescent emitter Y and the hostcompound(s) adds up to a total of 100% by weight and the singlet energyof the luminescent organomettalic complex X (E_(S1)(X)) is greater thanthe singlet energy of the fluorescent emitter Y (E_(S1)(Y)).

The difference of the singlet energy and the triplet energy of theluminescent organometallic complex X is preferably smaller than 0.1 eV,more preferably smaller than 0.05 eV.

Preferably, the emitting layer comprises 5 to 40% by weight of theluminescent organometallic complex X, 0.1 to 4.0% by weight of thefluorescent emitter Y and 94.9 to 56.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.More preferably, the emitting layer comprises 10 to 40% by weight of theluminescent organometallic complex X, 0.1 to 3.0% by weight of thefluorescent emitter Y and 89.9 to 57.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.Most preferred, the emitting layer comprises 20 to 40% by weight of theluminescent organometallic complex X, 0.1 to 3.0% by weight of thefluorescent emitter Y and 79.9 to 57.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.

The Luminescent Organometallic Complex (=Donor):

The luminescent organometallic complex X has a difference of the singletexcited state and the triplet excited state of smaller than 0.2 eV[Δ(E_(S1)(X))−(E_(T1)(X))<0.2 eV], especially of smaller than 0.1 eV,very especially of smaller than 0.05 eV. Therefore all organometalliccomplexes fulfilling this criteria are, in principle, suitable asluminescent organometallic complex X. Criteria, which help to identifymost adequate structures fulfilling the requirements stated above, aredescribed below:

i) For a fast energy transfer from the donor to the acceptor asignificant population of the S₁-state in the donor molecule is anecessary condition. This requires a very small S₁-T₁-splitting in thedonor molecule. In order to obtain these very small splittings thefrontier orbitals involved into the formation of the excited state atthe donor (typically HOMO and LUMO) have to be localized in spatiallydifferent regions of the molecule, thus minimizing the exchange integralK due to vanishing orbital overlap. For homoleptic iridium-complexesinvolving monoanionic bidentate ligands the degeneracy of the ligandshas to be lifted in order to induce interligand transitions in order tolocalize electrons in different regions of space as described above. Apreferred method is the synthesis of the C₁-symmetric meridionalcomplexes, where all three ligands have different bonding situations andtherefore different energies. Facial heteroleptic iridium-complexesinvolving monoanionic bidentate ligands can also be used to induceinter-ligand transitions by choosing ligands with different electroniclevels.

An important loss channel regarding quantum efficiency can be due todirect transfer of T₁-excitons from the donor molecule to thefluorescent acceptor. Although a significant singlet population in thedonor systems is expected as described above, still some tripletpopulation will be present. Triplet-transfer according to theDexter-mechanism (D. L. Dexter, J. Chem. Phys., 21, 836 (1953)) is ashort range process based on electron exchange mechanism between donorand acceptor. For an exchange interaction to be large a good overlapbetween the HOMOs of the donor and acceptor and simultaneously theoverlap of the LUMOs of the donor and acceptor is required. Also in thisrespect the spatial separation of HOMO and LUMO is beneficial. Standardquantum chemical calculations (DFT) can give a clear guidance here. Forexample, the orbital structure of BE-24 is localized and the the orbitalstructure of Ir(ppy)₃ is delocalized according to B3LYP/DZP-level oftheory.

ii) After the selection of organometallic complexes X according the thefirst selection criterion i) quantum chemical calculations to predictthe S₁-T₁-splitting should be carried out.

iii) Quantum chemically calculated S₁-T₁-splittings are verified bytemperature dependent emissive lifetime measurements.

In an embodiment of the present invention the luminescent organometalliccomplex X is a luminescent iridium complex. Suitable luminescent iridiumcomplexes are specified in the following publications: WO2006/056418A2,WO2007/115970, WO2007/115981, WO2008/000727, WO2009050281, WO2009050290,WO2011051404, US2011/057559 WO2011/073149, WO2012/121936A2,US2012/0305894A1, WO2012/170571, WO2012/170461, WO2012/170463,WO2006/121811, WO2007/095118, WO2008/156879, WO2008/156879,WO2010/068876, US2011/0057559, WO2011/106344, US2011/0233528,WO2012/048266, WO2012/172482 and European patent application no.14162805.7.

Preferably, the luminescent organometallic iridium complex X is aluminescent homoleptic meridional iridium carbene complex, or aluminescent heteroleptic iridium carbene complex.

The luminescent iridium complex is preferably a compound of formula

which are, for example, described in WO2011/073149, US2012/0305894,WO2012121936 and WO2012/172482, wherein the ligand(s) are each bidentateligands;

R¹ is a linear or branched alkyl radical optionally interrupted by atleast one heteroatom, optionally bearing at least one functional groupand having 1 to 20 carbon atoms, substituted or unsubstituted cycloalkylradical optionally interrupted by at least one heteroatom, optionallybearing at least one functional group and having 3 to 20 carbon atoms,substituted or unsubstituted aryl radical optionally interrupted by atleast one heteroatom, optionally bearing at least one functional groupand having 6 to 30 carbon atoms, substituted or unsubstituted heteroarylradical optionally interrupted by at least one heteroatom, optionallybearing at least one functional group and having a total of 5 to 18carbon atoms and/or heteroatoms, R², R³ and R⁴ are each independentlyhydrogen, a linear or branched alkyl radical optionally interrupted byat least one heteroatom, optionally bearing at least one functionalgroup and having 1 to 20 carbon atoms, substituted or unsubstitutedcycloalkyl radical optionally interrupted by at least one heteroatom,optionally bearing at least one functional group and having 3 to 20carbon atoms, substituted or unsubstituted aryl radical optionallyinterrupted by at least one heteroatom, optionally bearing at least onefunctional group and having 6 to 30 carbon atoms, substituted orunsubstituted heteroaryl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and havinga total of 5 to 18 carbon atoms and/or heteroatoms, group with donor oracceptor action, or

R² and R³ or R³ and R⁴ together with the carbon atoms to which they arebonded form an optionally substituted, saturated or unsaturated oraromatic ring optionally interrupted by at least one further heteroatomand having a total of 5 to 18 carbon atoms and/or heteroatoms, and mayoptionally be fused to at least one further optionally substitutedsaturated or unsaturated or aromatic ring optionally interrupted by atleast one further heteroatom and having a total of 5 to 18 carbon atomsand/or heteroatoms,

R⁶, R⁷, R⁸ and R⁹ are each independently hydrogen, a linear or branchedalkyl radical optionally interrupted by at least one heteroatom,optionally bearing at least one functional group and having 1 to 20carbon atoms, substituted or unsubstituted cycloalkyl radical optionallyinterrupted by at least one heteroatom, optionally bearing at least onefunctional group and having 3 to 20 carbon atoms, substituted orunsubstituted heterocycloalkyl radical optionally interrupted by atleast one heteroatom, optionally bearing at least one functional groupand having 3 to 20 carbon atoms and/or heteroatoms, substituted orunsubstituted aryl radical optionally interrupted by at least oneheteroatom, optionally bearing at least one functional group and having6 to 30 carbon atoms, substituted or unsubstituted heteroaryl radicaloptionally interrupted by at least one heteroatom, optionally bearing atleast one functional group and having a total of 5 to 18 carbon atomsand/or heteroatoms, group with donor or acceptor action, or R⁶ and R⁷,R⁷ and R⁸ or R⁸ and R⁹, together with the carbon atoms to which they arebonded, form a saturated, unsaturated or aromatic, optionallysubstituted ring which is optionally interrupted by at least oneheteroatom, has a total of 5 to 18 carbon atoms and/or heteroatoms, andmay optionally be fused to at least one further optionally substitutedsaturated or unsaturated or aromatic ring optionally interrupted by atleast one further heteroatom and having a total of 5 to 18 carbon atomsand/or heteroatoms, L is a monoanionic bidendate ligand,

n is 1, 2 or 3,

o is 0, 1 or 2, where, when o is 2, the L ligands may be the same ordifferent.

The homoleptic metal-carbene complexes may be present in the form offacial or meridional isomers, wherein the meridional isomers arepreferred.

A particularly preferred embodiment of the present invention thereforerelates to an OLED comprising at least one homoleptic metal-carbenecomplex of the general formula (IXa), (IXb), or (IXc) as luminescentorganometallic complex X, the homoleptic metal-carbene complex of theformula (IXa), (IXb), or (IXc) preferably being used in the form of themeridional isomer thereof.

In the case of the heteroleptic metal-carbene complexes, four differentisomers may be present.

Examples of particularly preferred luminescent iridium complexes arecompounds (BE-35a), (BE-1) to (BE-37) shown in claim 6. In addition,luminescent iridium complexes described in European patent applicationno. 14162805.7 are preferred. Among the luminescent iridium complexesdescribed in European patent application no. 14162805.7 iridiumcomplexes of formula

are more preferred, wherein X and Y are independently of each other CH,or N, with the proviso that at least one of X and Y is N;

R²³, R²⁴, R²⁷ and R²⁸ are each independently hydrogen; deuterium;methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, sec-butyl,iso-butyl, cyclopentyl, cyclohexyl, OCH₃, OCF₃; phenyl, pyridyl,primidyl, pyrazinyl, carbazolyl, dibenzofuranyl, dibenzothiophenyl,benzofuranyl and benzothiophenyl, wherein the aforementioned radicalsmay be unsubstituted or substituted by methyl, ethyl, n-propyl,iso-propyl, n-butyl, tert-butyl, sec-butyl, iso-butyl, methoxy, CF₃ orphenyl; a group with donor or acceptor action, selected from F, CF₃, CNand SiPh₃; and R²⁵ is methyl, ethyl, n-propyl, iso-propyl, n-butyl,tert-butyl, sec-butyl, iso-butyl, cyclopentyl, cyclohexyl, OCH₃, OCF₃;phenyl, pyridyl, primidyl, pyrazinyl, wherein the aforementionedradicals may be substituted by, preferably monosubstituted, by methyl,ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, sec-butyl, iso-butyl,methoxy or phenyl or unsubstituted; a group with donor or acceptoraction, selected from CF₃ and CN;

Examples of iridium complexes described in European patent applicationno. 14162805.7, which can advantageously be used as luminescent metalcomplex, are shown below.

Luminescent homoleptic meridional iridium carbene complexes arepreferred.

Among the luminescent iridium complexes (BE-1) to (BE-58) theluminescent iridium complexes (BE-2), (BE-3), (BE-24) and (BE-25) to(BE-58) are more preferred.

The homoleptic metal-carbene complexes may be present in the form offacial or meridional isomers, preference being given to the meridionalisomers.

In another preferred embodiment of the present invention the luminescentorganometallic complex X is a luminescent copper complex having adifference of the singlet energy (E_(S1)(X)) and the triplet energy(E_(T1)(X)) of smaller than 0.2 eV, especially 0.1 eV, very especially0.05 eV. Such luminescent copper complexes are, for example, describedin US2013264518, US2013150581, WO2013017675, WO2013007707, WO2013001086,WO2012156378, US2013025649, WO2013072508 and EP2543672.

US2013264518 and WO2013007707 discloses organic emitter molecules, thismolecules having a ΔE(S₁-T₁) value between the lowermost excited singletstate (S₁) and the triplet state beneath it (T₁) of less than 2500 cm⁻¹.

US2013150581 discloses neutral mononuclear copper(I) complexes for theemission of light with a structure according to formula

with:M: Cu(I);L∩L: a single negatively charged by bidentate ligand;N∩N: an diimine ligand, substituted with R and FG, in particular asubstituted 2,2′-bipyridine-derivative (bpy) or a1,10-phenanthroline-derivative (phen);R: at least one sterically demanding substituent for preventing a changeof geometry of copper(I) complexes towards a planarization in an exitedstate;FG=function group: at least a second substituent for conductingelectrons and for increasing the solubility in organic solvents, or atleast a second substituent for conducting holes and for increasing thesolubility in organic solvents, wherein the function group is boundeither directly or via a bridge to the diimine ligand;wherein the copper(l)complexhas a ΔE(S₁-T₁)-value between the lowest exited singlet (S₁)-state andthe triplet (T₁)-state below of smaller than 2500 cm⁻¹;an emission decay time of at the most 20 μs;an emission quantum yield of large 40%, anda solubility in organic solvents of at least 1 g/L.

WO2013017675 discloses dimeric copper

complexes, wherein: Cu: Cu(I), X: Cl, Br, I, SCN, CN, and/or alkinyl,and N∩P: a phosphane ligand substituted with an N-heterocycle.

WO2013072508 describes copper (I) complexes of the formula

where X*═Cl, Br, I, CN, OCN, SCN, alkinyl, and/or N₃ andN*∩E=a bidentate ligand, wherein E=a phosphanyl/arsenyl/antimonyl groupof the form R₂E (in which R=alkyl, aryl, heteroaryl, alkoxyl, phenoxyl,or amid);N*=an imin function that is a component of an aromatic group selectedfrom pyridyl, pyridazinyl, pyrimidyl, pyrazinyl, triazinyl, tetrazinyl,oxazolyl, thiazolyl, imidazolyl, pyrazolyl, isoxazolyl, isothiazolyl,1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,4-oxadiazolyl, 1,2,4-thiadiazolyl,tetrazolyl, 1,2,3,4-oxatriazolyl, 1,2,3,4-thiatriazolyl, chinolyl,isochinolyl, chinoxalyl, and chinazolyl, which are optionallyadditionally substituted and/or anneleated; and“∩”=at least one carbon atom that is likewise a component of thearomatic group, said carbon atom being found both directly adjacent tothe amine nitrogen atom as well as to the phosphorous, arsenic, orantimony atom; L represents specific monodentate, or bidentate ligands,such as, for example, copper complexes (Cu-3), (Cu-4) and (Cu-5) shownin claim 9. EP2543672 describes copper(I) complexes of formula

whereinX*: Cl, Br, I, CN and/or SCN; N*∩E=a bidentate ligand, wherein E=aphosphanyl/arsenyl group of the form R₂E (in which R=alkyl, aryl,heteroaryl, alkoxyl, phenoxyl, or amid);N*=an imin function that is a component of an N-heteroaromaticfive-membered ring selected from oxazolyl, imidazolyl, thiazolyl,isoxazolyl, isothiazolyl, pyrazolyl, 1,2,3-triazolyl, 1,2,3-oxadiazolyl,1,2,5-oxadiazolyl, 1,2,3-thiadiazolyl, and 1,2,5-thiadiazolyl;“∩”=at least one carbon atom that is likewise a component of thearomatic group, said carbon atom being found both directly adjacent tothe amine nitrogen atom as well as to the phosphorous, or arsenic atom;such as, for example, copper complex (Cu-2) shown in claim 9.WO2013001086 relates to a copper(I) complex of the formula

wherein X*═Cl, Br, I, CN, SCN, alkinyl, and/or N₃ (independently of oneanother); N*∩E=a bidentate ligand in which E=phosphanyl/arsenyl group ofthe form R₂E (in which R=alkyl, aryl, alkoxyl, phenoxyl, or amide);N*=imine function, which is a component of an N-heteroaromatic 5-ringthat is selected from the group consisting of pyrazole, isoxazole,isothiazole, triazole, oxadiazole, thiadiazole, tetrazole, oxatriazole,and thiatriazole; and “n”=at least one carbon atom which is likewise acomponent of the aromatic group, said carbon atom being located directlyadjacent both to the imine nitrogen atom as well as to the phosphor orarsenic atom.

Examples of luminescent copper complexes, which can advantageously beused according to the present invention are compounds (Cu-1) to (Cu-9)shown in claim 10.

Additional luminescent copper complexes are described, for example, inHartmut Yersin et al., J. Am. Chem. Soc. 136 (2014) 16032-6038, M.Hashimoto et al., J. Am. Chem. Soc. 133 (2011) 10348-10351, S. Harkinset al., J. Am. Chem. Soc. 130 (2008) 3478-3485 and S. Harkins et al., J.Am. Chem. Soc. 132 (2010) 9499-9508.

The copper complexes (Cu-1) to (Cu-11) can advantageously be used incombination with fluorescent emitters (FE-1), (FE-2), (FE-6), (FE-7),(FE-8) and (FE-9).

In addition, the Pd and Pt complexes with small S₁-T₁ splittingdescribed in WO2014109814 may be used as luminescent metal complex.

The Host Compound:

For efficient light emission the triplet energy of the host materialshould be larger than the triplet energy of the luminescentorganometallic complex X used. Therefore all host materials fulfillingthis requirement with respect to luminescent organometallic complex Xused are, in principle, suitable as host.

Suitable as host compounds are carbazole derivatives, for example4,4′-bis(carbazol-9-yl)-2,2′-dimethylbiphenyl (CDBP),4,4′-bis(carbazol-9-yl)biphenyl (CBP), 1,3-bis(N-carbazolyl)benzene(mCP), and the host materials specified in the following applications:WO2008/034758, WO2009/003919.

Further suitable host materials, which may be small molecules or(co)polymers of the small molecules mentioned, are specified in thefollowing publications: WO2007108459 (H-1 to H-37), preferably H-20 toH-22 and H-32 to H-37, most preferably H-20, H-32, H-36, H-37,WO2008035571 A1 (Host 1 to Host 6), JP2010135467 (compounds 1 to 46 andHost-1 to Host-39 and Host-43), WO2009008100 compounds No. 1 to No. 67,preferably No. 3, No. 4, No. 7 to No. 12, No. 55, No. 59, No. 63 to No.67, more preferably No. 4, No. 8 to No. 12, No. 55, No. 59, No. 64, No.65, and No. 67, WO2009008099 compounds No. 1 to No. 110, WO2008140114compounds 1-1 to 1-50, WO2008090912 compounds OC-7 to OC-36 and thepolymers of Mo-42 to Mo-51, JP2008084913 H-1 to H-70, WO2007077810compounds 1 to 44, preferably 1, 2, 4-6, 8, 19-22, 26, 28-30, 32, 36,39-44, WO201001830 the polymers of monomers 1-1 to 1-9, preferably of1-3, 1-7, and 1-9, WO2008029729 the (polymers of) compounds 1-1 to 1-36,WO20100443342 HS-1 to HS-101 and BH-1 to BH-17, preferably BH-1 toBH-17, JP2009182298 the (co)polymers based on the monomers 1 to 75,JP2009170764, JP2009135183 the (co)polymers based on the monomers 1-14,WO2009063757 preferably the (co)polymers based on the monomers 1-1 to1-26, WO2008146838 the compounds a-1 to a-43 and 1-1 to 1-46,JP2008207520 the (co)polymers based on the monomers 1-1 to 1-26,JP2008066569 the (co)polymers based on the monomers 1-1 to 1-16,WO2008029652 the (co)polymers based on the monomers 1-1 to 1-52,WO2007114244 the (co)polymers based on the monomers 1-1 to 1-18,JP2010040830 the compounds HA-1 to HA-20, HB-1 to HB-16, HC-1 to HC-23and the (co)polymers based on the monomers HD-1 to HD-12, JP2009021336,WO2010090077 the compounds 1 to 55, WO2010079678 the compounds H1 toH42, WO2010067746, WO2010044342 the compounds HS-1 to HS-101 and Poly-1to Poly-4, JP2010114180 the compounds PH-1 to PH-36, US2009284138 thecompounds 1 to 111 and H1 to H71, WO2008072596 the compounds 1 to 45,JP2010021336 the compounds H-1 to H-38, preferably H-1, WO2010004877 thecompounds H-1 to H-60, JP2009267255 the compounds 1-1 to 1-105,WO2009104488 the compounds 1-1 to 1-38, WO2009086028, US2009153034,US2009134784, WO2009084413 the compounds 2-1 to 2-56, JP2009114369 thecompounds 2-1 to 2-40, JP2009114370 the compounds 1 to 67, WO2009060742the compounds 2-1 to 2-56, WO2009060757 the compounds 1-1 to 1-76,WO2009060780 the compounds 1-1 to 1-70, WO2009060779 the compounds 1-1to 1-42, WO2008156105 the compounds 1 to 54, JP2009059767 the compounds1 to 20, JP2008074939 the compounds 1 to 256, JP2008021687 the compounds1 to 50, WO2007119816 the compounds 1 to 37, WO2010087222 the compoundsH-1 to H-31, WO2010095564 the compounds HOST-1 to HOST-61, WO2007108362,WO2009003898, WO2009003919, WO2010040777, US2007224446, WO06128800,WO2012014621, WO2012105310, WO2012/130709 and European patentapplications EP12175635.7 and EP12185230.5. and EP12191408.9 (inparticular page 25 to 29 of EP12191408.9).

The above-mentioned small molecules are more preferred than theabove-mentioned (co)polymers of the small molecules.

Further suitable host materials, are described in WO2011137072 (forexample,

best results are achieved if said compounds are combined with

WO2012048266 (for example,

WO2012162325 (for example,

and EP2551932 (for example,

In a particularly preferred embodiment, one or more compounds of thegeneral formula (X) specified hereinafter are used as host material.

wherein

X is NR, S, O or PR*;

R* is aryl, heteroaryl, alkyl, cycloalkyl, or heterocycloalkyl;

A²⁰⁰ is —NR²⁰⁶R²⁰⁷, —P(O)R²⁰⁸R²⁰⁹, —PR²¹⁰R²¹¹, —S(O)₂R²¹², —S(O)R²¹³,—SR²¹⁴, or —OR²¹⁵;

R²²¹, R²²² and R²²³ are independently of each other aryl, heteroaryl,alkyl, cycloalkyl, or heterocycloalkyl, wherein at least on of thegroups R²²¹, R²²², or R²²³ is aryl, or heteroaryl;

R²²⁴ and R²²⁵ are independently of each other alkyl, cycloalkyl,heterocycloalkyl, aryl, heteroaryl, a group A²⁰⁰, or a group havingdonor, or acceptor characteristics;

n2 and m2 are independently of each other 0, 1, 2, or 3;

R²⁰⁶ and R²⁰⁷ form together with the nitrogen atom a cyclic residuehaving 3 to 10 ring atoms, which can be unsubstituted, or which can besubstituted with one, or more substituents selected from alkyl,cycloalkyl, heterocycloalkyl, aryl, heteroaryl and a group having donor,or acceptor characteristics; and/or which can be annulated with one, ormore further cyclic residues having 3 to 10 ring atoms, wherein theannulated residues can be unsubstituted, or can be substituted with one,or more substituents selected from alkyl, cycloalkyl, heterocycloalkyl,aryl, heteroaryl and a group having donor, or acceptor characteristics;andR²⁰⁸, R²⁰⁹, R²¹⁰, R²¹¹, R²¹², R²¹³, R²¹⁴ and R²¹⁵ are independently ofeach other aryl, heteroaryl, alkyl, cycloalkyl, or heterocycloalkyl.Compounds of formula X, such as, for example,

are described in WO2010079051 (in particular pages on 19 to 26 and intables on pages 27 to 34, pages 35 to 37 and pages 42 to 43).

Additional host materials on basis of dibenzofurane are, for example,described in US2009066226, EP1885818B1, EP1970976, EP1998388 andEP2034538. Examples of particularly preferred host materials are shownbelow:

In the above-mentioned compounds T is O, or S, preferably O. If T occursmore than one time in a molecule, all groups T have the same meaning.Compounds SH-1 to SH-11 shown in claim 12 are most preferred.

The Fluorescent Emitter (=Acceptor):

The fluorescent emitter is preferably selected from the following:styrylamine derivatives, indenofluorene derivatives, polyaromaticcompounds, anthracene derivatives, tetracene derivatives, xanthenederivatives, perylene derivatives, phenylene derivatives, fluorenederivatives, arylpyrene derivatives, arylenevinylene derivatives,rubrene derivatives, coumarine derivatives, rhodamine derivatives,quinacridone derivatives, dicyanomethylenepyran derivatives, thiopyran,polymethine derivatives, pyrylium and thiapyrylium salts, periflanthenederivatives, indenoperylene derivatives, bis(azinyl)imineboroncompounds, bis(azinyl)methine compounds, carbostyryl compounds,monostyrylamines, distyrylamines, tristyrylamines, tetrastyrylamines,styrylphosphines, styryl ethers, arylamines, indenofluorenamines andindenofluorenediamines, benzoindenofluorenamines,benzoindenofluorenediamines, dibenzoindenofluorenamines,dibenzoindenofluorenediamines, substituted or unsubstitutedtristilbenamines, distyrylbenzene and distyrylbiphenyl derivatives,triarylamines, triazolo derivatves, naphthalene derivatives, anthracenederivatives, tetracene derivatives, fluorene derivatives, periflanthenederivatives, indenoperylene derivatives, phenanthrene derivatives,perylene derivatives, pyrene derivatives, triazine derivatives, chrysenederivatives, decacyclene derivatives, coronene derivatives,tetraphenylcyclopentadiene derivatives, pentaphenylcyclopentadienederivatives, fluorene derivatives, spirofluorene derivatives, pyranderivatives, oxazone derivatives, benzoxazole derivatives, benzothiazolederivatives, benzimidazole derivatives, pyrazine derivatives, cinnamicacid esters, diketopyrrolopyrrole derivatives, and acridone derivatives.

Fluorescent emitter compounds can preferably be polyaromatic compounds,such as, for example, 9,10-di(2-naphthylanthracene) and other anthracenederivatives, derivatives of tetracene, xanthene, perylene, such as, forexample, 2,5,8,11-tetra-t-butylperylene, phenylene, for example4,4′-(bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl, fluorene,arylpyrenes (US 2006/0222886), arylenevinylenes (U.S. Pat. No.5,121,029, U.S. Pat. No. 5,130,603), derivatives of rubrene, coumarine,rhodamine, quinacridone, such as, for example, N,N′-dimethylquinacridone(DMQA), dicyanomethylenepyrane, such as, for example, 4(dicyanoethylene)-6-(4-dimethylaminostyryl-2-methyl)-4H-pyrane (DCM),thiopyrans, polymethine, pyrylium and thiapyrylium salts, periflanthene,indenoperylene, bis(azinyl)imineboron compounds (US 2007/0092753 A1),bis(azinyl)methene compounds and carbostyryl compounds.

Furthermore preferred fluorescent emitter compounds can be emitterswhich are described in C. H. Chen et al.: “Recent developments inorganic electroluminescent materials” Macromol. Symp. 125, (1997), 1-48and “Recent progress of molecular organic electroluminescent materialsand devices” Mat. Sci. and Eng. R, 39 (2002), 143-222.

A monostyrylamine here is a compound which contains one substituted orunsubstituted styryl group and at least one, preferably aromatic, amine.A distyrylamine is preferably a compound which contains two substitutedor unsubstituted styryl groups and at least one, preferably aromatic,amine. A tristyrylamine is preferably a compound which contains threesubstituted or unsubstituted styryl groups and at least one, preferablyaromatic, amine. A tetrastyrylamine is preferably a compound whichcontains four substituted or unsubstituted styryl groups and at leastone, preferably aromatic, amine. The styryl group is particularlypreferably a stilbene, which may be further substituted. Thecorresponding phosphines and ethers which can be employed in accordancewith the invention are defined analogously to the amines. For thepurposes of this invention, arylamine or aromatic amine denotes acompound which contains three substituted or unsubstituted aromatic orheteroaromatic ring systems bonded directly to a nitrogen atom. At leastone of these aromatic or heteroaromatic ring systems can be a condensedring. Preferred examples thereof are aromatic anthracenamines, aromaticanthracenediamines, aromatic pyrenamines, aromatic pyrenediamines,aromatic chrysenamines and aromatic chrysenediamines. An aromaticanthracenamine can be a compound in which one diarylamine group isbonded directly to an anthracene group, preferably in position 9. Anaromatic anthracenediamine can be a compound in which two diarylaminegroups are bonded directly to an anthracene group, preferably inpositions 9 and 10. Aromatic pyrenamines, pyrenediamines, chrysenaminesand chrysenediamines are defined analogously thereto, in which thediarylamine groups on the pyrene are preferably bonded in position 1 orin positions 1 and 6.

Furthermore preferred fluorescent emitter compounds areindenofluorenamines and indenofluorenediamines, for example inaccordance with WO 2006/122630, benzoindenofluorenamines andbenzoindenofluorenediamines, for example in accordance with WO2008/006449, and dibenzoindenofluorenamines anddibenzoindenofluorenediamines, for example in accordance with WO2007/140847.

Examples of further fluorescent emitter compounds from the class of thestyrylamines which can be employed in accordance with the invention aresubstituted or unsubstituted tristilbenamines or those described in WO2006/000388, WO 2006/058737, WO 2006/000389, WO 2007/065549 and WO2007/115610. Distyrylbenzene and distyrylbiphenyl derivatives aredescribed in U.S. Pat. No. 5,121,029. Further styrylamines can be foundin US 2007/0122656 A1. Particularly preferred styrylamines andtriarylamines are the compounds of the formulae (183) to (188) and thosewhich are disclosed in U.S. Pat. No. 7,250,532 B2, DE 102005058557 A1,CN 1583691 A, JP 08053397 A, U.S. Pat. No. 6,251,531 B1, and US2006/210830 A.

Furthermore preferred fluorescent emitter compounds can be taken fromthe group of the triarylamines as disclosed in EP 1957606 A1 and US2008/0113101 A1.

Furthermore preferred fluorescent emitter compounds can be selected fromthe derivatives of naphthalene, anthracene, tetracene, fluorene,periflanthene, indenoperylene, phenanthrene, perylene (US 2007/0252517A1), pyrene, chrysene, decacyclene, coronene,tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, fluorene,spirofluorene, rubrene, coumarine (U.S. Pat. No. 4,769,292, U.S. Pat.No. 6,020,078, US 2007/0252517 A1), pyran, oxazone, benzoxazole,benzothiazole, benzimidazole, pyrazine, cinnamic acid esters,diketopyrrolopyrrole, acridone and quinacridone (US 2007/0252517 A1).

Of the anthracene compounds, the 9,10-substituted anthracenes, such as,for example, 9,10-diphenylanthracene and 9,10-bis(phenylethynyl)anthracene, are preferred. 1,4-Bis(9′-ethynylanthracenyl)benzene mayalso be preferred as fluorescent emitter compound.

Suitable fluorescent emitter units are furthermore the structuresdepicted in the following table, and the structures disclosed inJP06001973, WO2004047499, WO200505950, WO2006098080, WO2006114337, WO2007065678, US 20050260442, WO 2004092111, US2006251925, WO2007003520,WO2011040607; WO2011059099; WO2011090149, WO2011043083, WO2011086941;WO2011086935; JP 002001052870, EP373582, WO2006128800, WO2006/000388,WO2006/000389, WO06025273, WO2006/058737, WO2006/098080, WO2007/065549,WO2007/140847, WO2008/006449, WO2008/059713, WO2008/006449,WO2010122810, WO2011/052186, WO2013/185871, WO2014/037077,US2012/181520, KR2011/0041725, KR2011/0041728, KR2012/0011336,KR2012/0052499, KR2012/0074722 and KR2013/0110347.

Selection Criteria for Fluorescent Acceptors

i) Spectral Overlap

1-3% emission intensity, relative to the 100% emission maximum, is usedto determine the emission onset. For efficient energy transfer theemission onset of the fluorescent emitter (acceptor) should bered-shifted with respect to the emission onset of the luminescentorganometallic complex (donor) by 0 to 50 nm. Therefore all fluorescentemitters fulfilling this requirement with respect to luminescentorganometallic complex X are suitable as fluorescent emitter in thisinvention.

ii) Avoiding T₁-Transfer

An important loss channel regarding quantum efficiency can be due todirect transfer of T₁-excitons from the donor molecule to thefluorescent acceptor. Although a significant singlet population in thedonor systems described above is expected, still some triplet populationwill be present. Triplet-transfer according to the Dexter-mechanism (D.L. Dexter, J. Chem. Phys., 21, 836 (1953)) is a short range processbased on electron exchange mechanism between donor and acceptor. For anexchange interaction to be large a good overlap between the HOMOs of thedonor and acceptor and simultaneously the overlap of the LUMOs of thedonor and acceptor is required. To make this unwanted process asunlikely as possible, spatial separation of HOMO and LUMO on theacceptor should be achieved. Standard quantum chemical calculations(DFT) can give a clear guidance here. For example, the orbital structureof FE-7 is spatially separated and the orbital structure of FE-1 isdelocalized according to BP86/SV(P)-level of theory.

Another option is the sterical shielding of the acceptor chromophor toavoid any good overlap between donor and acceptor. FE-2 uses thisconcept to partly compensate for the lack of spatially separatedHOMO/LUMO.

Examples of the fluorescent emitter, which can be advantageously be usedaccording to the present invention are shown below:

The fluorescent emitters are commercially available at LuminescenceTechnology Corp. (Lumtec). The fluorescent emitters (FE-3) and (FE-4)can advantageously be used with iridium complexes of formula (XIa) and(XIb) as well as iridium complex (BE-26). The fluorescent emitter (FE-5)can advantageously be used with iridium complex (BE-26). The fluorescentemitters (FE-1), (FE-2), (FE-6), (FE-7), (FE-8) and (FE-9) canadvantageously be used with iridium complexes of formula (XIc).

The fluorescent emitters (FE-2) and (FE-7) are preferred, thefluorescent emitter (FE-7) is most preferred.

In a particularly preferred embodiment the emitting layer comprises

20 to 40% by weight of the luminescent organometallic complex X,

0.1 to 3.0% by weight of the fluorescent emitter Y and

79.9 to 57.0% by weight of a host compound(s), wherein the amount of theorganometallic complex X, the fluorescent emitter Y and the hostcompound(s) adds up to a total of 100% by weight.

The host compound can be one compound or it can be a mixture of two ormore compounds. Advantageously compounds HTM-1 and HTM-2 may be added asco-host.

The preferred combinations of host compound(s), luminescentorganometallic complex X and fluorescent emitter Y used in the emittinglayer are shown in the tables below:

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1aSH-4 BE-24 FE-6  1a SH-4 BE-24 FE-2  3a SH-4 BE-24 FE-7  4a SH-4 BE-24FE-8  5a SH-4 BE-24 FE-9  6a SH-4 BE-24 FE-1  7a SH-5 BE-24 FE-6  8aSH-5 BE-24 FE-2  9a SH-5 BE-24 FE-7 10a SH-5 BE-24 FE-8 11a SH-5 BE-24FE-9 12a SH-5 BE-24 FE-1 13a SH-11 BE-24 FE-1 14a SH-11 BE-24 FE-2 15aSH-11 BE-24 FE-6 16a SH-11 BE-24 FE-7 17a SH-11 BE-24 FE-8 18a SH-11BE-24 FE-9 19a SH-11 HTM-1 BE-24 FE-1 20a SH-5 HTM-1 BE-24 FE-6 21a SH-5HTM-1 BE-24 FE-2 22a SH-5 HTM-1 BE-24 FE-7 23a SH-5 HTM-1 BE-24 FE-8 24aSH-5 HTM-1 BE-24 FE-9 25a SH-5 HTM-2 BE-24 FE-6 26a SH-5 HTM-2 BE-24FE-2 27a SH-5 HTM-2 BE-24 FE-7 28a SH-5 HTM-2 BE-24 FE-8 29a SH-5 HTM-2BE-24 FE-9

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1bSH-4 BE-25 FE-6  2b SH-4 BE-25 FE-2  3b SH-4 BE-25 FE-7  4b SH-4 BE-25FE-8  5b SH-4 BE-25 FE-8  6b SH-4 BE-25 FE-1  7b SH-5 BE-25 FE-1  8bSH-5 BE-25 FE-2  9b SH-5 BE-25 FE-6 10b SH-5 BE-25 FE-7 11b SH-5 BE-25FE-8 12b SH-5 BE-25 FE-9 13b SH-11 BE-25 FE-1 14b SH-11 BE-25 FE-2 15bSH-11 BE-25 FE-6 18b SH-11 BE-25 FE-7 17b SH-11 BE-25 FE-8 18b SH-11BE-25 FE-9 19b SH-5 HTM-1 BE-25 FE-1 20b SH-5 HTM-1 BE-25 FE-2 21b SH-5HTM-1 BE-25 FE-6 22b SH-5 HTM-1 BE-25 FE-7 23b SH-5 HTM-1 BE-25 FE-8 24bSH-5 HTM-1 BE-25 FE-9 25b SH-5 HTM-2 BE-25 FE-1 26b SH-5 HTM-2 BE-25FE-2 27b SH-5 HTM-2 BE-25 FE-6 28b SH-5 HTM-2 BE-25 FE-7 29b SH-5 HTM-2BE-25 FE-8 30b SH-5 HTM-2 BE-25 FE-9

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1cSH-4 Cu-1 FE-1  2c SH-4 Cu-1 FE-2  3c SH-4 Cu-1 FE-6  4c SH-4 Cu-1 FE-7 5c SH-4 Cu-1 FE-8  6c SH-4 Cu-1 FE-9  7c SH-5 Cu-1 FE-1  8c SH-5 Cu-1FE-6  9c SH-5 Cu-1 FE-2 10c SH-5 Cu-1 FE-7 11c SH-5 Cu-1 FE-8 12c SH-5Cu-1 FE-9 13c SH-11 Cu-1 FE-6 14c SH-11 Cu-1 FE-2 15c SH-11 Cu-1 FE-716c SH-11 Cu-1 FE-8 17c SH-11 Cu-1 FE-9 18c SH-11 Cu-1 FE-1 19c SH-5HTM-1 Cu-1 FE-1 20c SH-5 HTM-1 Cu-1 FE-6 21c SH-5 HTM-1 Cu-1 FE-2 22cSH-5 HTM-1 Cu-1 FE-7 23c SH-5 HTM-1 Cu-1 FE-8 24c SH-5 HTM-1 Cu-1 FE-925c SH-5 HTM-2 Cu-1 FE-6 26c SH-5 HTM-2 Cu-1 FE-2 27c SH-5 HTM-2 Cu-1FE-7 28c SH-5 HTM-2 Cu-1 FE-8 29c SH-5 HTM-2 Cu-1 FE-9

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1dSH-1 BE-26 FE-3  2d SH-1 BE-26 FE-4  3d SH-1 BE-26 FE-5  4d SH-2 BE-26FE-3  5d SH-2 BE-26 FE-4  6d SH-2 BE-26 FE-5  7d SH-3 BE-26 FE-3  8dSH-3 BE-26 FE-4  9d SH-3 BE-26 FE-5 10d SH-4 BE-26 FE-3 11d SH-4 BE-26FE-4 12d SH-4 BE-26 FE-5 13d SH-5 BE-26 FE-3 14d SH-5 BE-26 FE-4 15dSH-5 BE-26 FE-5 16d SH-11 BE-26 FE-3 17d SH-11 BE-26 FE-4 18d SH-11BE-26 FE-5 19d SH-5 HTM-1 BE-26 FE-3 20d SH-5 HTM-1 BE-26 FE-4 21d SH-5HTM-1 BE-26 FE-5 22d SH-5 HTM-2 BE-26 FE-3 23d SH-5 HTM-2 BE-26 FE-4 24dSH-5 HTM-2 BE-26 FE-5

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1eSH-1 BE-3 FE-3  2e SH-1 BE-3 FE-4  3e SH-1 HTM-1 BE-3 FE-3  4e SH-2 BE-3FE-3  5e SH-2 BE-3 FE-4  6e SH-2 HTM-2 BE-3 FE-4  7e SH-3 BE-3 FE-3  8eSH-3 BE-3 FE-4  9e SH-3 HTM-2 BE-3 FE-3 10e SH-4 BE-3 FE-3 11e SH-4 BE-3FE-4 12e SH-4 HTM-1 BE-3 FE-4 13e SH-5 BE-3 FE-3 14e SH-5 BE-3 FE-4 15eSH-5 HTM-1 BE-3 FE-3 16e SH-5 HTM-2 BE-3 FE-3 17e SH-5 HTM-1 BE-3 FE-418e SH-5 HTM-2 BE-3 FE-4

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1fSH-4 BE-38 FE-6  2f SH-4 BE-38 FE-2  3f SH-4 BE-38 FE-7  4f SH-4 BE-38FE-8  5f SH-4 BE-38 FE-9  6f SH-4 BE-38 FE-1  7f SH-5 BE-38 FE-6  8fSH-5 BE-38 FE-2  9f SH-5 BE-38 FE-7 10f SH-5 BE-38 FE-8 11f SH-5 BE-38FE-9 12f SH-5 BE-38 FE-1 13f SH-11 BE-38 FE-1 14f SH-11 BE-38 FE-2 15fSH-11 BE-38 FE-6 18f SH-11 BE-38 FE-7 17f SH-11 BE-38 FE-8 18f SH-11BE-38 FE-9 19f SH-11 HTM-1 BE-38 FE-1 20f SH-5 HTM-1 BE-38 FE-6 21f SH-5HTM-1 BE-38 FE-2 22f SH-5 HTM-1 BE-38 FE-7 23f SH-5 HTM-1 BE-38 FE-8 24fSH-5 HTM-1 BE-38 FE-9 25f SH-5 HTM-2 BE-38 FE-6 26f SH-5 HTM-2 BE-38FE-2 27f SH-5 HTM-2 BE-38 FE-7 28f SH-5 HTM-2 BE-38 FE-8 29f SH-5 HTM-2BE-38 FE-9

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1gSH-1 BE-2 FE-3  2g SH-1 BE-2 FE-4  3g SH-1 BE-2 FE-5  4g SH-2 BE-2 FE-3 5g SH-2 BE-2 FE-4  6g SH-2 BE-2 FE-5  7g SH-3 BE-2 FE-3  8g SH-3 BE-2FE-4  9g SH-3 BE-2 FE-5 10g SH-4 BE-2 FE-3 11g SH-4 BE-2 FE-4 12g SH-4BE-2 FE-5 13g SH-5 BE-2 FE-3 14g SH-5 BE-2 FE-4 15g SH-5 BE-2 FE-5 16gSH-11 BE-2 FE-3 17g SH-11 BE-2 FE-4 18g SH-11 BE-2 FE-5 19g SH-5 HTM-1BE-2 FE-3 20g SH-5 HTM-1 BE-2 FE-4 21g SH-5 HTM-1 BE-2 FE-5 22g SH-5HTM-2 BE-2 FE-3 23g SH-5 HTM-2 BE-2 FE-4 24g SH-5 HTM-2 BE-2 FE-5

Organom. Fluorescent Device 1^(st) Host 2^(nd) Host Comp. Emitter  1hSH-1 BE-39 FE-3  2h SH-1 BE-39 FE-4  3h SH-1 BE-39 FE-5  4h SH-2 BE-39FE-3  5h SH-2 BE-39 FE-4  6h SH-2 BE-39 FE-5  7h SH-3 BE-39 FE-3  8hSH-3 BE-39 FE-4  9h SH-3 BE-39 FE-5 10h SH-4 BE-39 FE-3 11h SH-4 BE-39FE-4 12h SH-4 BE-39 FE-5 13h SH-5 BE-39 FE-3 14h SH-5 BE-39 FE-4 15hSH-5 BE-39 FE-5 16h SH-11 BE-39 FE-3 17h SH-11 BE-39 FE-4 18h SH-11BE-39 FE-5 19h SH-5 HTM-1 BE-39 FE-3 20h SH-5 HTM-1 BE-39 FE-4 21h SH-5HTM-1 BE-39 FE-5 22h SH-5 HTM-2 BE-39 FE-3 23h SH-5 HTM-2 BE-39 FE-4 24hSH-5 HTM-2 BE-39 FE-5Hole/Exciton Blocking Layer (f):

Blocking layers may be used to reduce the number of charge carriers(electrons or holes) and/or excitons that leave the emissive layer. Thehole blocking layer may be disposed between the emitting layer (e) andelectron transport layer (g), to block holes from leaving layer (e) inthe direction of electron transport layer (g). Blocking layers may alsobe used to block excitons from diffusing out of the emissive layer.Suitable hole/exciton material are, in principle, the host compoundsmentioned above. The same preferences apply as for the host material.

The at present most preferred hole/exciton blocking materials arecompounds SH-1 to SH-11.

Electron Transport Layer (g):

Electron transport layer may include a material capable of transportingelectrons. Electron transport layer may be intrinsic (undoped), ordoped. Doping may be used to enhance conductivity. Suitableelectron-transporting materials for layer (g) of the inventive OLEDscomprise metals chelated with oxinoid compounds, such astris(8-hydroxyquinolato)aluminum (Alq₃), compounds based onphenanthroline such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline(DDPA=BCP), 4,7-diphenyl-1,10-phenanthroline (Bphen),2,4,7,9-tetraphenyl-1,10-phenanthroline,4,7-diphenyl-1,10-phenanthroline (DPA) or phenanthroline derivativesdisclosed in EP1786050, in EP1970371, or in EP1097981, and azolecompounds such as 2-(4-biphenylyl)-5-(4-t-butylphenyl)-1,3,4-oxadiazole(PBD) and 3-(4-biphenylyl)-4phenyl-5-(4-t-butylphenyl)-1,2,4-triazole(TAZ).

It is likewise possible to use mixtures of at least two materials in theelectron-transporting layer, in which case at least one material iselectron-conducting. Preferably, in such mixed electron-transportinglayers, at least one phenanthroline compound is used, preferably BCP, orat least one pyridine compound according to the formula (VIII) below.More preferably, in mixed electron-transporting layers, in addition toat least one phenanthroline compound, alkaline earth metal or alkalimetal hydroxyquinolate complexes, for example Liq, are used. Suitablealkaline earth metal or alkali metal hydroxyquinolate complexes arespecified below (formula VII). Reference is made to WO2011/157779.

The electron-transporting layer may also be electronically doped inorder to improve the transport properties of the materials used, inorder firstly to make the layer thicknesses more generous (avoidance ofpinholes/short circuits) and in order secondly to minimize the operatingvoltage of the device. Electronic doping is known to those skilled inthe art and is disclosed, for example, in W. Gao, A. Kahn, J. Appl.Phys., Vol. 94, No. 1, 1 Jul. 2003 (p-doped organic layers); A. G.Werner, F. Li, K. Harada, M. Pfeiffer, T. Fritz, K. Leo, Appl. Phys.Lett., Vol. 82, No. 25, 23 Jun. 2003 and Pfeiffer et al., OrganicElectronics 2003, 4, 89-103 and K. Walzer, B. Maennig, M. Pfeiffer, K.Leo, Chem. Soc. Rev. 2007, 107, 1233. For example, it is possible to usemixtures which lead to electrical n-doping of the electron-transportinglayer. n-Doping is achieved by the addition of reducing materials. Thesemixtures may, for example, be mixtures of the abovementioned electrontransport materials with alkali/alkaline earth metals or alkali/alkalineearth metal salts, for example Li, Cs, Ca, Sr, Cs₂CO₃, with alkali metalcomplexes, for example 8-hydroxyquinolatolithium (Liq), and with Y, Ce,Sm, Gd, Tb, Er, Tm, Yb, Li₃N, Rb₂CO₃, dipotassium phthalate, W(hpp)₄from EP1786050, or with compounds described in EP1837926B1, EP1837927,EP2246862 and WO2010132236.

In a preferred embodiment, the electron-transporting layer comprises atleast one compound of the general formula (VII)

in whichR³² and R³³ are each independently F, C₁-C₈-alkyl, or C₆-C₁₄-aryl, whichis optionally substituted by one or more C₁-C₈-alkyl groups, ortwo R³² and/or R³³ substituents together form a fused benzene ring whichis optionally substituted by one or more C₁-C₈-alkyl groups;a and b are each independently 0, or 1, 2 or 3,M¹ is an alkaline metal atom or alkaline earth metal atom,p is 1 when M¹ is an alkali metal atom, p is 2 when M¹ is an earthalkali metal atom.

A very particularly preferred compound of the formula (VII) is

which may be present as a single species, or in other forms such asLi_(g)Q_(g) in which g is an integer, for example Li₆Q₆. Q is an8-hydroxyquinolate ligand or an 8-hydroxyquinolate derivative.

In a further preferred embodiment, the electron-transporting layercomprises at least one compound of the formula (VIII),

in whichR³⁴, R³⁵, R³⁶, R³⁷, R^(34′), R^(35′), R^(36′) and R^(37′) are eachindependently H, C₁-C₁₈-alkyl, C₁-C₁₈-alkyl which is substituted by Eand/or interrupted by D, C₆-C₂₄-aryl, C₆-C₂₄-aryl which is substitutedby G, C₂-C₂₀-heteroaryl or C₂-C₂₀-heteroaryl which is substituted by G,Q is an arylene or heteroarylene group, each of which is optionallysubstituted by G;D is —CO—; —COO—; —S—; —SO—; —SO₂—; —O—; —NR⁴⁰—; —SiR⁴⁵R⁴⁶—; —POR⁴⁷—;—CR³⁸═CR³⁹—; or —C≡C—;E is —OR⁴⁴; —SR⁴⁴; —NR⁴⁰R⁴¹; —COR⁴³; —COOR⁴²; —CONR⁴⁰R⁴¹; —CN; or F;G is E, C₁-C₁₈-alkyl, C₁-C₁₈-alkyl which is interrupted by D,C₁-C₁₈-perfluoroalkyl, C₁-C₁₈-alkoxy, or C₁-C₁₈-alkoxy which issubstituted by E and/or interrupted by D,in whichR³⁸ and R³⁹ are each independently H, C₆-C₁₈-aryl; C₆-C₁₈-aryl which issubstituted by C₁-C₁₈-alkyl or C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; orC₁-C₁₈-alkyl which is interrupted by —O—;R⁴⁰ and R⁴¹ are each independently C₆-C₁₈-aryl; C₆-C₁₈-aryl which issubstituted by C₁-C₁₈-alkyl or C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; orC₁-C₁₈-alkyl which is interrupted by —O—; orR⁴⁰ and R⁴¹ together form a 6-membered ring;R⁴² and R⁴³ are each independently C₆-C₁₈-aryl; C₆-C₁₈-aryl which issubstituted by C₁-C₁₈-alkyl or C₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; orC₁-C₁₈-alkyl which is interrupted by —O—,R⁴⁴ is C₆-C₁₈-aryl; C₆-C₁₈-aryl which is substituted by C₁-C₁₈-alkyl orC₁-C₁₈-alkoxy; C₁-C₁₈-alkyl; or C₁-C₁₈-alkyl which is interrupted by—O—,R⁴⁵ and R⁴⁶ are each independently C₁-C₁₈-alkyl, C₆-C₁₈-aryl orC₆-C₁₈-aryl which is substituted by C₁-C₁₈-alkyl,R⁴⁷ is C₁-C₁₈-alkyl, C₆-C₁₈-aryl or C₆-C₁₈-aryl which is substituted byC₁-C₁₈-alkyl.

Preferred compounds of the formula (VIII) are compounds of the formula(VIIIa)

in which Q is:

R⁴⁸ is H or C₁-C₁₈-alkyl and

R^(48′) is H, C₁-C₁₈-alkyl or

Particular preference is given to a compound of the formula

In a further, very particularly preferred embodiment, theelectron-transporting layer comprises a compound Liq and a compoundETM-2.

In a preferred embodiment, the electron-transporting layer comprises thecompound of the formula (VII) in an amount of 99 to 1% by weight,preferably 75 to 25% by weight, more preferably about 50% by weight,where the amount of the compounds of the formulae (VII) and the amountof the compounds of the formulae (VIII) adds up to a total of 100% byweight.

The preparation of the compounds of the formula (VIII) is described inJ. Kido et al., Chem. Commun. (2008) 5821-5823, J. Kido et al., Chem.Mater. 20 (2008) 5951-5953 and JP2008/127326, or the compounds can beprepared analogously to the processes disclosed in the aforementioneddocuments.

It is likewise possible to use mixtures of alkali metal hydroxyquinolatecomplexes, preferably Liq, and dibenzofuran compounds in theelectron-transporting layer. Reference is made to WO2011/157790.Dibenzofuran compounds A-1 to A-36 and B-1 to B-22 described inWO2011/157790 are preferred, wherein dibenzofuran compound

is most preferred.

In a preferred embodiment, the electron-transporting layer comprises Liqin an amount of 99 to 1% by weight, preferably 75 to 25% by weight, morepreferably about 50% by weight, where the amount of Liq and the amountof the dibenzofuran compound(s), especially ETM-1, adds up to a total of100% by weight.

In a preferred embodiment, the electron-transporting layer comprises atleast one phenanthroline derivative and/or pyridine derivative.

In a further preferred embodiment, the electron-transporting layercomprises at least one phenanthroline derivative and/or pyridinederivative and at least one alkali metal hydroxyquinolate complex.

In a further preferred embodiment, the electron-transporting layercomprises at least one of the dibenzofuran compounds A-1 to A-36 and B-1to B-22 described in WO2011/157790, especially ETM-1.

In a further preferred embodiment, the electron-transporting layercomprises a compound described in WO2012/111462, WO2012/147397,WO2012014621, such as, for example, a compound of formula

US2012/0261654, such as, for example, a compound of formula

and WO2012/115034, such as for example, such as, for example, a compoundof formula

Electron Injection Layer (h):

The electron injection layer may be any layer that improves theinjection of electrons into an adjacent organic layer.Lithium-comprising organometallic compounds such as8-hydroxyquinolatolithium (Liq), CsF, NaF, KF, Cs₂CO₃ or LiF may beapplied between the electron transport layer (g) and the cathode (i) asan electron injection layer (h) in order to reduce the operatingvoltage.

Cathode (i):

The cathode (i) is an electrode which serves to introduce electrons ornegative charge carriers. The cathode may be any metal or nonmetal whichhas a lower work function than the anode. Suitable materials for thecathode are selected from the group consisting of alkali metals of group1, for example Li, Cs, alkaline earth metals of group 2, metals of group12 of the Periodic Table of the Elements, comprising the rare earthmetals and the lanthanides and actinides. In addition, metals such asaluminum, indium, calcium, barium, samarium and magnesium, andcombinations thereof, may be used.

In general, the different layers, if present, have the followingthicknesses:

anode (a): 500 to 5000 Å (angstrom), preferably 1000 to 2000 Å;

a hole injection layer (b): 50 to 1000 Å, preferably 200 to 800 Å,

hole-transport layer (c): 50 to 1000 Å, preferably 100 to 900 Å,

exciton blocking layer (d): 10 to 500 Å, preferably 50 to 100 Å,

light-emitting layer (e): 10 to 1000 Å, preferably 50 to 600 Å,

a hole/exciton blocking layer (f): 10 to 500 Å, preferably 50 to 100 Å,

electron-transport layer (g): 50 to 1000 Å, preferably 200 to 800 Å,

electron injection layer (h): 10 to 500 Å, preferably 20 to 100 Å,

cathode (i): 200 to 10 000 Å, preferably 300 to 5000 Å.

The inventive OLED can be produced by methods known to those skilled inthe art. In general, the inventive OLED is produced by successive vapordeposition of the individual layers onto a suitable substrate. Suitablesubstrates are, for example, glass, inorganic semiconductors or polymerfilms. For vapor deposition, it is possible to use customary techniques,such as thermal evaporation, chemical vapor deposition (CVD), physicalvapor deposition (PVD) and others. In an alternative process, theorganic layers of the OLED can be applied from solutions or dispersionsin suitable solvents, employing coating techniques known to thoseskilled in the art.

The OLEDs can be used in all apparatus in which electroluminescence isuseful. Suitable devices are preferably selected from stationary andmobile visual display units and illumination units. Stationary visualdisplay units are, for example, visual display units of computers,televisions, visual display units in printers, kitchen appliances andadvertising panels, illuminations and information panels. Mobile visualdisplay units are, for example, visual display units in cellphones,tablet PCs, laptops, digital cameras, MP3 players, vehicles anddestination displays on buses and trains. Further apparatus in which theinventive OLEDs can be used are, for example, keyboards; items ofclothing; furniture; wallpaper.

Accordingly, the present invention relates to an apparatus selected fromthe group consisting of stationary visual display units such as visualdisplay units of computers, televisions, visual display units inprinters, kitchen appliances and advertising panels, illuminations,information panels, and mobile visual display units such as visualdisplay units in cellphones, tablet PCs, laptops, digital cameras, MP3players, vehicles and destination displays on buses and trains;illumination units; keyboards; items of clothing; furniture; wallpaper,comprising at least one inventive organic light-emitting device, oremitting layer.

Another aspect of the invention is an emitting layer, comprising

2 to 40% by weight of a luminescent organometallic complex X having adifference of the singlet energy and the triplet energy of smaller than0.2 eV,

0.05 to 5% by weight of a fluorescent emitter Y and

55 to 97.95% by weight of a host compound(s), wherein the amount of theorganometallic complex X, the fluorescent emitter Y and the hostcompound(s) adds up to a total of 100% by weight and the singlet energyof the luminescent organometallic complex X (E_(S1)(X)) is greater thanthe singlet energy of the fluorescent emitter Y (E_(S1)(Y)).

The difference of the singlet energy and the triplet energy of theluminescent organometallic complex X is preferably smaller than 0.1 eV,more preferably smaller than 0.05 eV.

Preferably, the emitting layer comprises 5 to 40% by weight of theluminescent organometallic complex X, 0.1 to 4.0% by weight of thefluorescent emitter Y and 94.9 to 56.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.More preferably, the emitting layer comprises 10 to 40% by weight of theluminescent organometallic complex X, 0.1 to 3.0% by weight of thefluorescent emitter Y and 89.9 to 57.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.Most preferred, the emitting layer comprises 20 to 40% by weight of theluminescent organometallic complex X, 0.1 to 3.0% by weight of thefluorescent emitter Y and 79.9 to 57.0% by weight of a host compound(s),wherein the amount of the organometallic complex X, the fluorescentemitter Y and the host compound(s) adds up to a total of 100% by weight.

Another subject of the present invention is the use of a fluorescentemitter Y for doping an emitting layer comprising a luminescentorganometallic complex X having a difference of the singlet energy(E_(S1)(X)) and the triplet energy (E_(T1)(X)) of smaller than 0.2 eVand having a singlet energy (E_(S1)(X)) which is greater than thesinglet energy of the fluorescent emitter Y (E_(S1)(Y)) and a hostcompound(s) to decrease the emissive lifetime τ₀ below 100 ns, which iscalculated by τ₀=τ_(v)/QY, of thin films consisting of the luminescentorganometallic complex X, fluorescent emitter Y and host compound(s).The decrease of the emissive lifetime τ₀ below 100 ns take place withoutsacrificing QY. i.e. the EQE remains fundamentally the same, or isimproved.

The emissive lifetime τ₀ is preferably in the range of 0.1 to 80 ns,more preferably 0.5 to 50 ns, most preferred 0.5 to 40 ns.

The difference of the singlet energy and the triplet energy of theluminescent organometallic complex X is preferably smaller than 0.1 eV,more preferably smaller than 0.05 eV.

The emitting layer can be used in light-emitting electrochemical cells(LEECs), OLEDs, OLED sensors, especially in a gas and vapor sensor nothermetically sealed from the outside, optical temperature sensors,organic solar cells (OSCs; organic photovoltaics, OPVs), organicfield-effect transistors, organic diodes and organic photodiodes.

The following examples are included for illustrative purposes only anddo not limit the scope of the claims. Unless otherwise stated, all partsand percentages are by weight.

EXAMPLES

The examples which follow, more particularly the methods, materials,conditions, process parameters, apparatus and the like detailed in theexamples, are intended to support the present invention, but not torestrict the scope of the present invention. All experiments are carriedout in protective gas atmosphere. The percentages and ratios mentionedin the examples below—unless stated otherwise—are % by weight and weightratios. The meridionale isomers of BE-2, BE-3, BE-24, BE-25, BE-26,BE-38, BE-39 and BE-40 are used in the Examples.

Determination of Quantum Efficiencies and Emissive Wavelengths (PMMAMatrix)

The photoluminescence (PL) spectra of the emissive donor and/or emissiveacceptor molecule are measured on thin polymer films doped with therespective molecules. The thin films are prepared by the followingprocedure: a 10%-w/w polymer solution is made by dissolving 1 g of thepolymer “Plexiglas 6N” (Evonik) in 9 g of dichloromethane, followed bystirring for one hour. The respective molecules are added to the PMMAsolution according to the desired doping concentrations, and stirring iscontinued for one minute. The solutions are cast by doctor-blading witha film applicator (Model 360 2082, Erichsen) with a 60 μm gap ontoquartz substrates providing thin doped polymer films (thickness ca. 6μm).

Determination of Quantum Efficiencies and Emissive Wavelengths (SH-11Matrix)

The same procedure described above for the PMMA matrix is used, exceptthat instead of the PMMA polymer 4.8 mg of the host molecule (SH-11) aredissolved in 250 μl dichloromethane, followed by stirring for one hour.

The PL spectra and quantum yields (QY) of these films are measured withthe integrating-sphere method using the absolute PL Quantum YieldMeasurement System (Hamamatsu, Model C9920-02) (excitation wavelength:370 nm for table 1, 310 nm for tables 2-9).

Determination of the Excited-State Lifetime τ_(V) and the EmissiveLifetime τ₀

The excited-state lifetime (T_(v)) of the prepared films is measured bythe following procedure: For excitation a pulsed diode laser withexcitation wavelength 310 nm operated at 10 kHz is used. Detection iscarried out with time correlated single photon counting (TCSPC). Theemissive lifetime τ₀ is calculated by τ₀=τ_(v)/QY.

The luminescent organometallic complex BE-24 is used as donor. Thefluorescent emitters FE-1 and FE-2 are used as acceptor.

Table 1 shows four series of energy transfer experiments involving thedonor molecule BE-24 in two different concentrations, two differentacceptor molecules (FE-1 and FE-2) and two different host molecules(PMMA and SH-11). Donor Acc. c(Don.) c(Acc.) Host τ_(v)/ns τ_(o)/ns QYλ_(max, em) BE-24 FE-1 2%   0% PMMA 700 875 80% 440 nm BE-24 FE-1 0%0.10% PMMA 4 4 98% 468 nm BE-24 FE-1 2% 0.05% PMMA 49 83 78% 468 nmBE-24 FE-1 2% 0.10% PMMA 44 57 77% 466 nm BE-24 FE-1 2% 0.20% PMMA 27 3871% 469 nm BE-24 FE-1 2% 0.40% PMMA 17 25 68% 470 nm BE-24 FE-1 10%   0% PMMA 700 843 83% 447 nm BE-24 FE-1 10%  0.05% PMMA 69 103 67% 468nm BE-24 FE-1 10%  0.10% PMMA 57 89 64% 468 nm BE-24 FE-1 10%  0.20%PMMA 25 48 52% 473 nm BE-24 FE-1 10%  0.40% PMMA 24 49 49% 473 nm BE-24FE-1 2%   0% SH-11 — 71% 449 nm BE-24 FE-1 2% 0.05% SH-11 57 98 58% 453nm BE-24 FE-1 2% 0.10% SH-11 40 70 57% 454 nm BE-24 FE-1 2% 0.30% SH-1117 31 55% 458 nm BE-24 FE-2 0% 0.10% PMMA 5 5 100%  458 nm BE-24 FE-2 2%0.10% PMMA 240 282 85% 460 nm BE-24 FE-2 2%   2% PMMA 20 27 74% 487 mn

The first part of the table shows samples with 2% of the donor BE-24 andvarying concentrations of the acceptor FE-1 in the host PMMA. The firstline shows that the pure donor (2% doping concentration) has anexcited-state lifetime (τ_(v)) of 700 ns in combination with a quantumyield of 80% and an emission maximum at 440 nm. The pure acceptor(doping concentration of 0.1%) has an excited-state lifetime of 3.7 nsat ˜100% quantum efficiency. The emission maximum is at 468 nm. Usingnow the donor as well as the acceptor as dopands it is shown that a veryefficient energy transfer from the donor to the acceptor occurs (78%quantum efficiency with 0.1% acceptor doping compared to 80% withoutacceptor doping).

The shift in the emission maximum from 440 nm (donor) to 468-470 nm(acceptor) supports this interpretation (see FIGS. 2 and 3). It is shownin the table that the excited-state lifetime is reduced to as little as17 ns without substantially sacrificing quantum efficiency.

In the second part of the table the donor concentration is increased to10%. An overall similar behavior is observed as described for the 2%doping concentration, however with smaller quantum efficiencies.

The third part of table 1 describes a system, where PMMA is replaced bythe host material SH-11. FE-1 is significantly blue shifted by ˜15 nmrelative to PMMA. Again the same basic trends are shown including areduction of the excited-state lifetime below 20 ns for 0.3% of thefluorescent acceptor, FE-1. Even with the very small difference inemission wavelength between donor and acceptor an efficient transferoccurs.

In the fourth part another fluorescent acceptor molecule is introduced(FE-2). Here significantly higher concentrations of the acceptormolecule are necessary. With 2% concentration of FE-2 high quantumefficiencies of 74% are achieved in combination with 20 ns excited-statelifetime.

Quantum Yield (QY) (%), CIE_(x,y), and emissive lifetime τ₀ (ns)measured for different samples are shown in the Tables 2 to 9 below.Excitation for determining the QY is carried out at 310 nm, here theabsorption is almost exclusively from the donor.

TABLE 2 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% BE-24, x % FE-7 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 1 0 79 0.156 0.1481030 Film 2 0.2 96 0.158 0.267 43 Film 3 0.5 98 0.161 0.307 24 Film 41.0 99 6.170 0.374 9

TABLE 3 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% BE-24, x % FE-2 and 90-x% SH-11. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 5 0 89 0.179 0.2001320 Film 6 0.5 78 0.138 0.226 40 Film 7 1.0 72 0.138 0.235 39

TABLE 4 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% BE-38, x % FE-2 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 8 0 62 0.157 0.177934 Film 9 0.5 72 0.135 0.230 46 Film 10 1.0 64 0.131 0.260 25

TABLE 5 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% BE-38. x % FE-7 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 11 0 62 0.157 0.177934 Film 12 0.2 75 0.158 0.266 46 Film 13 0.5 83 0.162 0.316 21 Film 141.0 89 0.170 0.370 9

TABLE 6 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% BE-40, x % FE-4 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 15 0 76 0.325 0.556877 Film 16 1.0 87 0.379 0.595 79

TABLE 7 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% BE-39, x % FE-5 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 17 0 86 0.222 0.419976 Film 18 0.2 97 0.262 0.621 31 Film 19 0.5 96 0.289 0.641 15 Film 201.0 94 0.304 0.642 10

TABLE 8 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% Cu-1, x % FE-2 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 21 0 47 0.171 0.21532125 Film 22 0.2 67 0.143 0.231 41 Film 23 0.5 77 0.136 0.243 36 Film24 1.0 83 0.132 0.259 29

TABLE 9 Quantum Yield (QY) (%), CIE_(x, y,) and emissive lifetime τ₀(ns) measured for a thin film consisting of 10% Cu-1, x % FE-7 and 90-x% PMMA. Example x/% QY/% CIE_(x) CIE_(y) τ₀/ns Film 25 0 47 0.171 0.21532125 Film 26 0.2 72 0.163 0.302 1.6 Film 27 0.5 86 0.166 0.351 1.5 Film28 1.0 92 0.171 0.385 1.7

As evident from tables 2 to 9 the emissive lifetime τ₀ can be reduced bythe inventive concept to values well below 80 ns while maintaining oreven increasing the QY. The CIE_(y) coordinate shows that efficienttransfer takes place already at low concentrations, as the emissioncomes from the acceptor.

Determination of the S₁-T₁ Splitting

To determine the S₁-T₁-splitting we use a combined approach involvingtemperature dependent determination of excited-state lifetimes andquantum chemical calculations.

a) Experimental Approach:

A 60 μm thin film of the Iridium complex in PMMA (2%) is prepared bydoctor blading from dichloromethane onto a quartz substrate. A cryostat(Optistat CF, Oxford Instruments) is used for cooling the sample withliquid helium. The PL spectra and the PL decay time at the maximum ofthe emission are measured with a spectrometer (Edinburgh Instruments FLS920P) at the following temperatures: 4K, 10K, 20K, 30K, 50K, 75K, 100K,150K, 200K, 250K, 300K, 350K, 375K, 400K.

Fitting:

The temperature dependence of the averaged PL decay time providesinformation about the energy levels and decay rates of different statesthat are populated according to the Boltzmann distribution (M. J. Leitl,V. A. Krylova, P. I. Djurovich, M. E. Thompson, H. Yersin J. Am. Chem.Soc. 2014, 136, 16032-16038; T. Hofbeck, H. Yersin, Inorg. Chem. 2010,49, 9290-9299). For a system with two populated excited states thefollowing expression can be fitted to the measured data k_(av) vs T:

$\begin{matrix}{k_{av} = \frac{k_{I} + {k_{II}e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}}}{1 + e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

For a system with three populated excited states equation 2 is used.

$\begin{matrix}{k_{av} = \frac{k_{I} + {k_{II}e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}}} + {k_{III}e^{{- \Delta}\; E_{I,{III}}{I{({k_{B}T})}}}}}{1 + e^{{- \Delta}\; E_{I,{II}}{I{({k_{B}T})}}} + e^{{- \Delta}\; E_{I,{III}}{I{({k_{B}T})}}}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$where k_(av) is the decay rate determined from the measurement, k_(I),k_(II), k_(III) are the decay rates of the respective excited states,E_(I,II) and E_(I,III) are the energy differences of the excited statesI and II compared to the lowest excited state, k_(B) is the Boltzmannconstant and T is the temperature.

A high value of k (>2*10⁶ s⁻¹) is an indication that the respectiveexcited state is a singlet. However, since the spin multiplicity of theexcited states cannot be proven by PL measurements, additional quantumchemical calculations have to be carried out and compared to theexcited-state levels we find from the fitting of the measurement.

b) Quantum Chemical Approach

First the triplet geometries of the potential donor molecules wereoptimized at the unrestricted BP86 [J. P. Perdew, Phys. Rev. B 33, 8822(1986) and J. P. Perdew, Phys. Rev. B 33, 8822 (1986)]/SV(P) [A.Schäfer, H. Horn, and R. Ahlrichs, J. Chem. Phys. 9, 2571 (1992)]-levelof theory including effective core potentials in case of iridiumtransition metal complexes [D. Andrae, U. Haeussermann, M. Dolg, H.Stoll, and H. Preuss, Theor. Chim. Acta 77, 123 (1990)]. Based on thesetriplet geometries relativistic all electron calculations were performedto determine the S₁-T₁-splitting. Specifically we used theB3LYP-functional [Becke, A. D., J. Chem. Phys. 98, 5648 (1993)] incombination with an all-electron basis set of double zeta quality [E.van Lenthe and E. J. Baerends, J. Comp. Chemistry 24, 1142 (2003)].Scalar relativistic effects were included at the SCF level via the ZORAapproach [E. van Lenthe, A. E. Ehlers and E. J. Baerends, Journal ofChemical Physics 110, 8943 (1999)]. Based on that wavefunction timedependent density functional calculations were performed including spinorbit coupling via perturbation theory [F. Wang and T. Ziegler, Journalof Chemical Physics 123, 154102 (2005)]. The S₁-T₁-splitting is thenfinally determined as the energy difference of the lowest T₁-sublevel tothe first spin-orbit corrected S₁-state. Relativistic calculations werecarried out using the ADF program package [3. ADF2009.01, SCM,Theoretical Chemistry, Vrije Universiteit, Amsterdam, The Netherlands,http://www.scm.com] whereas for the geometry optimisations the TURBOMOLEprogram package [R. Ahlrichs, M. Bär, M. Häser, H. Horn, and C. Cölmel,Chem. Phys. Lett. 162, 165 (1989)] was used.

To illustrate the validity of the approach a comparison betweenexperimentally fitted and calculated S₁-T₁-levels is given in the Table10 below: ΔE(S₁-T₁) [eV] ΔE(S₁-T₁) [eV] Molecular Structure AbbreviationIsomer experimental calculated

Ir(ppy)₃ fac ~0.200 0.150

FIrpic trans-N,N ~0.300 0.180

BE-24 mer 0.010 0.038

BE-38 mer 0.057

BE-2 mer 0.035

BE-3 mer 0.026

BE-26 mer 0.034

BE-25 mer 0.040

A very good agreement between calculated and fitted data was obtained.The exceptionally small S₁-T₁-splitting of BE-24 was clearly shown.Ir(ppy)₃ and Flrpic are included for extended comparison.S₁-T₁-splittings for Ir(ppy)₃ and Flrpic were taken from BurakHimmetoglu, Alex Marchenko, Ismaïla Dabo, and Matteo Cococcioni, TheJournal of Chemical Physics 137, 154309 (2012) and literature citedtherein. Please note, the S₁-T₁-splittings for Ir(ppy)₃ and Flrpic arevery approximate in nature due to their determination from peakwavelengths/absorption onsets. Both theory and measurements also agreefor these molecules in giving S₁-T₁-splittings significantly larger than0.1 eV.

Determination of the S₁-T₁-Splitting of BE-24

Quantum chemical calculations as well as low temperaturephotoluminescence measurements are performed in order to determine theS₁-T₁-splitting of compound (BE-24). By employing the following set ofequations (1)-(4)

$\begin{matrix}{k_{av} = {{\frac{n_{s_{1}}}{n}k_{S_{1}}} + {\frac{n_{T_{1}}}{n}k_{T_{1}}}}} & (1) \\{n_{S_{1}} = e^{- \frac{\Delta\; E{({S_{1} - T_{1}})}}{k\; T}}} & (2) \\{n_{T_{1}} = 1} & (3) \\{n = {n_{S_{1}} + n_{T_{1}}}} & (4)\end{matrix}$and identifying the rate at 4 K with the T₁-rate one can fit the S₁emissive rate and the S₁-T₁-splitting simultaneously. We obtain anemissive lifetime of 330 ns for the S₁-state, 10 μs for the T₁-state and0.01 eV for the S₁-T₁-splitting. This exceptionally small value leads toan Boltzmann-population of the S₁-state of ˜70%, thus also explainingthe very efficient energy transfer described in the preceding section.Since the spin multiplicity of the states cannot be directly proven bythe PL measurements we carried out additional relativistic quantumchemical calculations. Here we find in agreement with the aboveinterpretation a very small S₁-T₁-splitting of 0.04 eV.

Application Examples

The ITO substrate used as the anode is cleaned first with commercialdetergents for LCD production (Deconex® 20NS, and 25ORGAN-ACID®neutralizing agent) and then in an acetone/isopropanol mixture in anultrasound bath. To eliminate possible organic residues, the substrateis exposed to a continuous ozone flow in an ozone oven for a further 25minutes. This treatment also improves the hole injection properties ofthe ITO. Thereafter, the organic materials specified below are appliedby vapor deposition to the cleaned substrate at about 10⁻⁷-10⁻⁹ mbar ata rate of approx. 0.5-5 nm/min.

The hole injection, conductor and exciton blocker applied to thesubstrate is

with a thickness between 60 and 100 nm, of which the 50 to 90 nm aredoped with MoO₃. The remaining 10 nm of Ir(DPBIC)₃ serve as an excitonblocker. Subsequently, the emission layer (EML) is deposited as amixture of luminescent organometallic complex BE-X (2 to 40% by wt.),fluorescent emitter FE-X (0.05 to 2.0% by wt.) and host compound

or

(58 to 97.95% by wt.) by vapor deposition with a thickness of 40 nm.Subsequently, SH-11 or SH-2 is applied by vapor deposition with athickness of 5 nm as a hole blocker.

Next, as an electron transporting layer, a mixture of

(50:50) is applied by vapor deposition (25 to 35 nm). Then, following 4nm of KF deposition by vapor deposition, a 100 nm-thick Al electrode isfinally deposited by thermal evaporation. All components areadhesive-bonded to a glass lid in an inert nitrogen atmosphere.

Comparative Application Example 1 and Application Example 1

Comparative Device 1 has the following architecture:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-1/SH-11 (2:0:98)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nm KF-100nm Al

Devices 1 is obtained in analogy to Comparative Device 1. The devicearchitecture of Device 1 is shown below:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-1/SH-11 (2:0.05:97.95)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

To characterize the OLED, electroluminescence spectra are recorded atvarious currents and voltages. In addition, the current-voltagecharacteristic is measured in combination with the luminance todetermine luminous efficiency and external quantum efficiency (EQE).Driving voltage U and EQE are given at luminance (L)=1000 cd/m² andCommission Internationale de l'Éclairage (CIE) coordinate are given at 5mA/cm² except otherwise stated. Furthermore, 50% lifetime (LT50) ismeasured at constant current density J=25 mA/cm², the time spent untilthe initial luminance is reduced to 50%. EQE and LT50 of the ComparativeApplication Examples are set to 100 and EQE and LT50 of the ApplicationExamples are specified in relation to those of the ComparativeApplication Examples.

TABLE 11 EQE LT50 BE-24 FE-1 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl. 20 98 100 0.164 0.156 100 Ex. 1 Comp. Device 1 Appl. Ex. 1 2 0.05 97.95128 0.157 0.143 135 Device 1

Comparative Application Example 2 and Application Examples 2 and 3

Comp. Device 2 and Devices 2 and 3 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 2 andDevices 2 and 3 are shown below:

Comp. Device 2:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-1/SH-11 (10:0:90)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 2:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-1/SH-11 (10:0.05:89.95)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 3:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-1/SH-11 (10:0.1:89.9)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 12 EQE LT50 BE-24 FE-1 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.10 0 90 100 0.164 0.165 100 Comp. Device 2 Appl. Ex. 2 10 0.05 89.95 1050.157 0.146 120 Device 2 Appl. Ex. 3 10 0.1 89.9 101 0.156 0.143 120Device 3

Comparative Application Example 3 and Application Examples 4 and 5

Comp. Device 3 and Devices 4 and 5 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 3 andDevices 4 and 5 are shown below:

Comp. Device 3:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (30:0:70)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 4:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (30:0.1:69.9)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 5:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (30:0.3:69.7)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 13 EQE LT50 BE-24 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.30 0 70 100 0.153 0.153 100 Comp. Device 3 Appl. Ex. 4 30 0.1 69.9 1070.147 0.146 175 Device 4 Appl. Ex. 5 30 0.3 69.7 99 0.140 0.144 340Device 5

Comparative Application Example 4 and Application Examples 6 and 7

Comp. Device 4 and Devices 6 and 7 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 4 andDevices 6 and 7 are shown below:

Comp. Device 4:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (30:0:70)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 6:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (30:1:69)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 7:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (30:2:68)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 14 EQE LT50 BE-24 FE-7 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.30 0 70 100 0.152 0.167 100 Ex. 4 Comp. Device 4 Appl. Ex. 6 30 1 69 1200.148 0.240 800 Device 6 Appl. Ex. 7 30 2 68 107 0.149 0.273 2515 Device7

Comparative Application Example 5 and Application Examples 8 to 10

Comp. Device 5 and Devices 8 to 10 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 5 andDevices 8 to 10 are shown below:

Comp. Device 5:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (40:0:60)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 8:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (40:0.1:59.9)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 9:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (40:0.3:59.7)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 10:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (40:0.5:59.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 15 EQE LT50 BE-24 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.40 0 60 100 0.155 0.200 100 Ex. 5 Comp. Device 5 Appl. Ex. 8 40 0.1 59.9120 0.147 0.188 180 Device 8 Appl. Ex. 9 40 0.3 59.7 123 0.139 0.168 310Device 9 Appl. Ex. 10 40 0.5 59.5 111 0.135 0.168 535 Device 10

Comparative Application Example 6 and Application Examples 11 to 15

Comp. Device 6 and Devices 11 to 15 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 6 andDevices 11 to 15 are shown below:

Comp. Device 6:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (40:0:60)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 11:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (40:0.3:59.7)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 12:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (40:0.5:59.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 13:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (40:0.7:59.3)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 14:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (40:1:59)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 15:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-7/SH-11 (40:2:58)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 16 EQE LT50 BE-24 FE-7 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.40 0 60 100 0.152 0.188 100 Ex. 6 Comp. Device 6 Appl. Ex. 11 40 0.359.7 102 0.149 0.199 245 Device 11 Appl. Ex. 12 40 0.5 59.5 110 0.1480.222 355 Device 12 Appl. Ex. 13 40 0.7 59.3 114 0.148 0.251 580 Device13 Appl. Ex. 14 40 1 59 108 0.149 0.274 910 Device 14 Appl. Ex. 15 40 258 103 0.151 0.293 1190 Device 15

Comparative Application Example 7 and Application Example 16

Comp. Device 7 and Device 16 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 7 andDevice 15 are shown below:

Comp. Device 7:

ITO-50 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nm BE-2/FE-5/SH-2(10:0:90)-5 nm SH-2-35 nm ETM-1:Liq (50:50)-4 nm KF-100 nm Al

Device 16:

ITO-50 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nm BE-2/FE-5/SH-2(10:0.3:99.7)-5 nm SH-2-35 nm ETM-1:Liq (50:50)-4 nm KF-100 nm Al

TABLE 17 EQE LT50 BE-2 FE-5 SH-2 [%] CIE_(x) CIE_(y) [%] Comp. Appl. 100 90 100 0.368 0.554 100 Ex. 7 Comp. Device 7 Appl. Ex. 18 10 0.3 89.7110 0.296 0.594 165 Device 16

Comparative Application Example 8 and Application Examples 17 and 18

Comp. Device 8 and Devices 17 to 19 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 8 andDevice 17 and 18 are shown below:

Comp. Device 8:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (30:0:70)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 17:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (30:0.5:69.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 18:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (30:1:69)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 18 EQE LT50 BE-38 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.30 0 70 100 0.163 0.216 100 Ex. 8 Comp. Device 8 Appl. Ex. 17 30 0.569.5 182 0.140 0.157 120 Device 17 Appl. Ex. 18 30 1 69 167 0.137 0.154180 Device 18

Comparative Application Example 9 and Application Examples 19 to 21

Comp. Device 8 and Devices 19 to 21 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 9 andDevice 19 to 21 are shown below:

Comp. Device 9:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (30:0:70)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 19:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (30:0.5:69.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 20:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (30:1:69)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 21:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (30:2:68)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 19 EQE LT50 BE-38 FE-7 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.30 0 70 100 0.161 0.19 100 Ex. 9 Comp. Device 9 Appl. Ex. 19 30 0.5 69.5121 0.156 0.195 220 Device 19 Appl. Ex. 20 30 1 69 148 0.155 0.221 370Device 20 Appl. Ex. 21 30 2 68 150 0.156 0.247 505 Device 21

Comparative Application Example 10 and Application Example 22

Comp. Device 10 and Device 22 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 10 andDevice 22 are shown below:

Comp. Device 10:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (40:0:70)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 22:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (40:0.5:59.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 20 EQE LT50 BE-38 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.40 0 60 100 0.164 0.215 100 Ex. 10 Comp. Device 10 Appl. Ex. 22 40 0.559.5 144 0.141 0.157 175 Device 22

Comparative Application Example 11 and Application Examples 22 to 24

Comp. Device 11 and Devices 22 to 24 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 11 andDevice 22 to 24 are shown below:

Comp. Device 11:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (40:0:60)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 22:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (40:0.5:59.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 23:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (40:1:59)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 24:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-7/SH-11 (40:2:58)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 21 EQE LT50 BE-38 FE-7 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.40 0 60 100 0.167 0.229 100 Ex. 11 Comp. Device 11 Appl. Ex. 22 40 0.559.5 123 0.158 0.208 125 Device 22 Appl. Ex. 23 40 1 59 164 0.156 0.230225 Device 23 Appl. Ex. 24 40 2 58 169 0.156 0.263 320 Device 24

Comparative Application Example 12 and Application Examples 25 and 26

Comp. Device 12 and Devices 25 and 26 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 12 andDevice 25 and 26 are shown below:

Comp. Device 12:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (10:0:90)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 25:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (10:0.1:89.9)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 26:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (10:0.5:89.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 22 EQE LT50 BE-24 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.10 0 90 100 0.152 0.129 100 Ex. 12 Comp. Device 12 Appl. Ex. 25 10 0.189.9 112 0.148 0.142 120 Device 25 Appl. Ex. 26 10 0.5 89.5 151 0.1390.156 405 Device 26

Comparative Application Example 13 and Application Examples 27 and 28

Comp. Device 13 and Devices 27 and 28 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 13 andDevice 27 and 28 are shown below:

Comp. Device 13:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (20:0:80)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 27:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (20:0.1:79.9)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 28:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-24/FE-2/SH-11 (20:0.5:79.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 23 EQE LT50 BE-24 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.20 0 80 100 0.154 0.172 100 Ex. 13 Comp. Device 13 Appl. Ex. 27 20 0.179.9 127 0.144 0.155 240 Device 27 Appl. Ex. 28 20 0.5 79.5 116 0.1350.160 770 Device 28

Comparative Application Example 14 and Application Examples 29 and 30

Comp. Device 14 and Devices 29 and 30 are obtained in analogy to Comp.Application Example 1. The device architectures of Comp. Device 14 andDevice 29 and 30 are shown below:

Comp. Device 14:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (20:0:80)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 29:

ITO-90 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (20:0.5:79.5)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 30:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (20:1:79)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

Device 31:

ITO-80 nm Ir(DPBIC)₃:MoO₃ (90:10)-10 nm Ir(DPBIC)₃-40 nmBE-38/FE-2/SH-11 (20:2:78)-5 nm SH-11-25 nm ETM-1:Liq (50:50)-4 nmKF-100 nm Al

TABLE 24 EQE LT50 BE-38 FE-2 SH-11 [%] CIE_(x) CIE_(y) [%] Comp. Appl.20 0 80 100 0.162 0.201 100 Ex. 14 Comp. Device 14 Appl. Ex. 29 20 0.579.5 193 0.142 0.163 165 Device 29 Appl. Ex. 30 20 1.0 79.0 185 0.1380.163 230 Device 30 Appl. Ex. 31 20 2.0 78.0 169 0.137 0.163 315 Device31

As evident from Tables 11 to 24 the EQE and/or lifetime of devices ofthe present invention, comprising organometallic complex X, fluorescentemitter Y and host compound(s), is increased in comparison to devices,comprising only organometallic complex X and host compound(s).

By doping, for example, an emitting layer containing a luminescentorganometallic complex having a small S₁-T₁ splitting, with afluorescent emitter the emission decay time can significantly beshortened without sacrificing external quantum efficiency (EQE) becauseof very efficient energy transfer.

The invention claimed is:
 1. An organic light-emitting device comprising(a) an anode, (i) a cathode, and (e) an emitting layer between the anodeand cathode, comprising 2 to 40% by weight of a luminescentorganometallic complex X having a difference of the singlet energy(E_(S1)(X)) and the triplet energy (E_(T1)(X)) of smaller than 0.2 eV,0.05 to 5.0% by weight of a fluorescent emitter Y, and 55 to 97.95% byweight of a host compound(s), wherein the amount of the luminescentorganometallic complex X, the fluorescent emitter Y and the hostcompound(s) does not exceed a total of 100% by weight, and wherein thesinglet energy of the luminescent organometallic complex X (E_(S1)(X))is greater than the singlet energy of the fluorescent emitter Y(E_(S1)(Y)).
 2. The organic light-emitting device according to claim 1,wherein the difference of the singlet energy and the triplet energy ofthe luminescent organometallic complex X is smaller than 0.1 eV.
 3. Theorganic light-emitting device according to claim 1, wherein thedifference of the singlet energy and the triplet energy of theluminescent organometallic complex X is smaller than 0.05 eV.
 4. Theorganic light-emitting device according to claim 1, wherein the emissivelifetime τ₀, which is calculated by τ₀=τ_(v)/QY, of thin filmsconsisting of the luminescent organometallic complex X, fluorescentemitter Y and host compound(s) is below 100 ns.
 5. The organiclight-emitting device according to claim 1, wherein the luminescentorganometallic complex X is a luminescent iridium complex.
 6. Theorganic light-emitting device according to claim 5, wherein theluminescent iridium complex is a compound of formulae


7. The organic light-emitting device according to claim 5, wherein theluminescent iridium complex is a compound of formulae

wherein X and Y are independently of each other CH, or N, with theproviso that at least one of X and Y is N; R²³, R²⁴, R²⁷ and R²⁸ areeach independently hydrogen, deuterium, methyl, ethyl, n-propyl,iso-propyl, n-butyl, tert-butyl, sec-butyl, iso-butyl, cyclopentyl,cyclohexyl, OCH₃, OCF₃, phenyl, pyridyl, primidyl, pyrazinyl,carbazolyl, dibenzofuranyl, dibenzothiophenyl, benzofuranyl andbenzothiophenyl, wherein the aforementioned radicals may beunsubstituted or substituted by methyl, ethyl, n-propyl, iso-propyl,n-butyl, tert-butyl, sec-butyl, iso-butyl, methoxy, CF₃ or phenyl, agroup with donor or acceptor action, selected from F, CF₃, CN and SiPh₃;and R²⁵ is methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl,sec-butyl, iso-butyl, cyclopentyl, cyclohexyl, OCH₃, OCF₃, phenyl,pyridyl, primidyl, pyrazinyl, wherein the aforementioned radicals may besubstituted by, preferably monosubstituted, by methyl, ethyl, n-propyl,iso-propyl, n-butyl, tert-butyl, sec-butyl, iso-butyl, methoxy or phenylor unsubstituted; a group with donor or acceptor action selected fromCF₃ and CN.
 8. The organic light-emitting device according to claim 1,wherein the luminescent organometallic complex X is a luminescent coppercomplex.
 9. The organic light-emitting device according to claim 8,wherein the luminescent copper complex is a compound of formulae


10. The organic light-emitting device according to claim 1, wherein thefluorescent emitter Y is a compound of formulae


11. The organic light-emitting device according to claim 1, wherein thehost compound is a compound of formulae

wherein T is O, or S.
 12. The organic light-emitting device according toclaim 11, wherein the host compound is a compound of formulae


13. The organic light-emitting device according to claim 1, comprisingin this order: (a) an anode, (b) optionally a hole injection layer, (c)a hole transport layer, (d) exciton blocking layer (e) an emittinglayer, comprising the luminescent organometallic complex X thefluorescent emitter Y and the host compound(s), (f) a hole/excitonblocking layer (g) an electron transport layer, (h) optionally anelectron injection layer, and (i) a cathode.
 14. An emitting layer,comprising 2 to 40% by weight of a luminescent organometallic complex Xhaving a difference of the singlet energy and the triplet energy ofsmaller than 0.2 eV, 0.05 to 5% by weight of a fluorescent emitter Y and55 to 97.95% by weight of a host compound(s), wherein the amount of theorganometallic complex X, the fluorescent emitter Y and the hostcompound(s) does not exceed a total of 100% by weight and the singletenergy of the luminescent organometallic complex X (E_(S1)(X)) isgreater than the singlet energy of the fluorescent emitter Y(E_(S1)(Y)).
 15. An apparatus selected from the group consisting ofstationary visual display units such as visual display units ofcomputers, televisions, visual display units in printers, kitchenappliances and advertising panels, illuminations, information panels,and mobile visual display units such as visual display units incellphones, laptops, digital cameras, MP3 players, vehicles anddestination displays on buses and trains; illumination units; keyboards;items of clothing; furniture; wallpaper, comprising the organiclight-emitting device according to claim
 1. 16. An apparatus selectedfrom the group consisting of stationary visual display units such asvisual display units of computers, televisions, visual display units inprinters, kitchen appliances and advertising panels, illuminations,information panels, and mobile visual display units such as visualdisplay units in cellphones, laptops, digital cameras, MP3 players,vehicles and destination displays on buses and trains; illuminationunits; keyboards; items of clothing; furniture; wallpaper, comprisingthe emitting layer of claim
 14. 17. A light-emitting electrochemicalcell (LEEC), organic light emitting device (OLED) sensor, an organicsolar cell (OSC), an organic field-effect transistor, an organic diodeand an organic photodiode, comprising the emitting layer of claim 14.